Chapter 3.9, Problem 1EQ

Suppose you sell short 100 shares of stock initially selling for $100 a share. Your initial margin requirement is 50% of the value of the stock. You receive no interest on The funds placed in your margin account.
a. How much do you need to contribute to your margin account?
b. What will be your rate of return for the following stock prices at the end of a one-year holding period.
(assume the stock pays no dividends)? (i) $90; (ii) 100; (iii) 110.