Suppose you are buying stocks on margin. The margin requirement is $40\%$ while the maintenance margin is $20\%.$ Right now, you put $$800$ of your own money and the stock you want to buy today has a price of $$50$ per share.

a$.$ How many shares of stock can you buy if you trade on margin?

b$.$ What is your own equity percentage when the stock price turns out to be $$60?$

c$.$ What is the margin call price for you?