You purchased shares of Broussard Company using 50 percent margin; you invested a total of $20,000 (buying 1,000 shares of a price of $20 per share) by using $10,000 of your own funds and borrowing $10,000. Determine your percentage profit or loss under the following situations (ignore borrowing costs, dividends, and taxes):

a. The stock price rises to $23 a share

b. The stock price rises to $30 a share

c. The stock price falls to $16 a share

d. The stock price falls to $10 a share