A: You buy 100 shares of stock at $50 per share on margin of 40%. If the price of the stock rises to $60, what is your percentage gain in equity?

B: You sell short 100 Shares of a stock at $60 per share. How much is your initial margin (equity) given current margin requirements of 40%? If the stock declines to $30 per share, what is your percentage gain or loss on the initial equity? If the minimum margin requirements are 30%, at what price would you have a margin call?