You purchase 100 shares of stock at $100 ($10,000); the margin requirement is 40 percent. What are

Question:

You purchase 100 shares of stock at $100 ($10,000); the margin requirement is 40 percent. What are the dollar and percentage returns if
a. You sell the stock for $112 and buy the stock for cash?
b. You sell the stock for $90 and buy the stock on margin?
c. You sell the stock for $60 and buy the stock on margin?