Sally has $18,960 in her investment account. She buys 2,000 shares of DEF Inc. for $12.00 per share. The margin requirement for DEF is 30%. a. How much in excess of the minimum requirement did Sally contribute to the purchase of these shares? (1 mark) Number b. Assuming Sally does not contribute any more margin to her account, below what price will Sally first face a margin call? Ignore interest and transaction costs. (3 marks) Number