a) Define broker and market maker (dealer). Explain the key differences between these two roles. (10 marks) b) Based on a recent lawsuit news of Cactus plc, Ms. Jones contacted her broker and decided to sell short 500 shares of Cactus plc common stock at $37 per share. The initial margin is 75%. 1) Define short selling. (5 marks) 2) What is Ms. Jones' percent margin if the stock price increases to $55 per share in a week? (5 marks) 3) Assume the maintenance margin is 60%, at what stock price would Ms. Jones receive a margin call? (5 marks)