1. A stock sells for $10 per share. You purchase 100 shares for $10 a share (i.e., for $1,000), and after a year the price rises to $17.50. What will be the percentage return on your investment if you bought the stock on margin and the margin requirement was (a) 25 percent, (b) 50 percent, and (c) 75 percent? (Ignore commissions, dividends, and interest expense.)

2. Repeat Problem 1 to determine the percentage return on your investment but in this case suppose the price of the stock falls to $7.50 per share. What generalization can be inferred from your answers to Problems 1 and 2?

3. An investor sells a stock short for $36 a share. A year later, the investor covers the position at $30 a share. If the margin requirement is 60 percent, what is the percentage return earned on the investment? Redo the calculations, assuming the price of the stock is $42 when the investor closes the position.