What is the irony in "The Gift of the Magi"?

Irony is a literary device that occurs when the author uses elements of the story, like plot or character development, setting, or action to show contrast or the opposite of what the characters or the author may be feeling. 

Here's an example--  In "Rhyme of the Ancient Mariner," there is a line that says "Water, water every where, not any drop to drink."  This is an example of irony, because the ship is in the middle of the ocean.  Yes, the crew is surrounded by water, but they can not drink any of it.  Ah, the irony!

What is the difference between revenue under perfect competition and monopoly?there should be four differences atleast

Are you asking difference between the way the revenue of a firm is determined under conditions of perfect competition and monopoly.

Under both these condition a firm sells as much product as it can till its marginal revenue equals marginal costs and and any further increase will result in increasing the marginal cost. However, the point at which this point is determined for a firm operating in a perfectly competitive market and a monopoly firm are different.

Under the condition of perfect competition, a single firm has no control over either the market equilibrium price or the total market demand. The firm can sell as much as it wants to at the market equilibrium price, but cannot sell any thing at prices above this price. Under this condition the marginal revenue of the firm is same as the market price, irrespective of the level of revenue. Under these condition the firm will continue to increase its profit by increasing its sale as long as the sales price, which is same as its marginal revenue, is higher than the marginal cost. Thus the company will continue to increase its revenue till its marginal cost equals market equilibrium price. This also results in the firm operating at a level that results in minimum average cost for the firm in long run.

The situation faced by the Monopoly firm is different. For a monopoly firm its marginal revenue is always less than the sales price at any level of revenue, as any increase in price reduces the total quantity sold. Thus marginal revenue falls as the total revenue increases. For this reason, for a monopoly firm, the marginal revenue equals marginal cost at a level of revenue that is less than the level where marginal cost is lower than average cost, and the firm is not producing at minimum cost.

Some critics view this tale from a feminist viewpoint. What are some examples of this view?

Mental illness and depression was not widely understood during this period of time and treatment for these unfortunate individuals bordered on barbaric. Mary, the main character, suffers from post-partum depression. Prior to her illness, she was an active writer, but this activity is forbidden when Mary is forced to endure the "rest cure". " Her husband, John, who is a doctor, misidentifies her condition and prescribes a “rest cure” made popular by the well-respected physician Weir Mitchell. The rest cure assumes that intellectual stimulation damages a woman physically and psychologically, so John requires the narrator to stop all writing, all reading, and essentially, all higher-level thinking" (e-notes).Mary secretly begins writing her story, documenting the tragic and horrible side effects of the "rest cure". Unfortunately, Mary's post partum depression coupled with her lack of mental stimulation and compassion she begins a downward spiral into madness.The author's (Charlotte Perkins)feminist point-of-view can be seen in her philosophies, "the oppression of women is ultimately based on women’s economic dependence on men. Other institutions—religion, education, ethics, marriage and family—simply reinforce this relationship" (e-notes). Some of her view points (I let you ferret these out.) would be considered inflamatory today.

In Macbeth, how do the witches contribute further to Macbeth's downfall when he revisits them in scene 16?

I assume you are reffering to Act IV, scene i when Macbeth seeks out the witches to get advice and find out more of his fate. The significance here is that Macbeth is seeking the witches out this time. He is taking control of his own terrible fate and the witches acknowledge this, saying "By the pricking of my thumbs, / Something wicked this way comes." Instead of hapless victim, Macbeth is an instrument in his own downfall.

The prophecies of the witches both encourage Macbeth, since he feels that they grant him immortality, but they are paradoxically troubling, too. After all, if cannot be defeated--since every man is born of a woman and forests grow very slowly--why would Banquo's sons be shown as kings? Macbeth chooses to select the information that benefits him and ignore (as much as he can) the rest.

The bottom line here is that it is Macbeth making the decisions. He does not appear to be under the witches' power or spell here and Lady Macbeth is nowhere to be found. This is Macbeth choosing his fate.

What events in "The Most Dangerous Game" constitute the falling action?

The falling action, which comes right after the climax, would be after Rainsford leaps off a cliff and into the ocean, to what Zaroff believes is his death. The hunt had been escalating up to that point. Zaroff, disappointed, heads home, has dinner, and retires to his room for the night. Rainsford, all the while is hiding behind the curtains in his room waiting to surprise him with the fact that Rainsford indeed has beaten Zaroff. The men exchange words and Zaroff leaves the house the loser of his own game for the first time and goes out into the night where he falls victim to his own hounds. 

If I need to write a cover letter for Beowulf, who should I write it to? And what kind of job can apply for today's world? Again, my teacher wants...

It might be interesting to make Beowulf's job something that is unrelated to war and survival.  After all, many of his traits - independence, tenacity, strong sense of duty, compassion, leadership - are traits that would be helpful in any number of jobs.

For example, wouldn't Beowulf make an interesting teacher?  Or perhaps a company president?  Or even a salesman - consider his determination, especially when holding on to Grendel's arm.! 

Once you've picked your job:

1. Start with a salutation (Dear ________,)

2. Have Beowulf introduce himself and his main qualities.

3. He should then announce what he is writing for.

4. Next paragraph, go through why he is good for this position.  List examples from his "previous jobs"

5. Final paragraph, explain why he is interested in the job and thank the reader.

What is the theme of Black Beauty?

The theme is the main topic, idea, or message in a piece of writing.

The theme of Black Beauty is most definitely that horses (as well as all animals and also people) ought to be treated kindly, ethically and humanely.

The book is about the life story and experiences of a horse called Black Beauty who is treated well by his owner in the beginning of his life but is later mistreated by other owners. The story describes how horses were often treated badly in Victorian England and how the animals suffered injury and sometimes even death due to the mistreatment.

The book also underlines issues of social class, inequality and wide differences between the poor and rich in England at that time. The book was so influential after it was published in 1877 that it even contributed to the eradication of the bearing rein. This was a rein used to pull horses' heads back, causing them pain.