You have borrowed $20,000 on margin to buy shares in TPG, which are now selling at $20 per share. Your account starts at the initial margin requirement of 50%. The maintenance margin is 35%. Two days later, the share price falls to $18 per share. How low can the price of TPG shares fall before you receive a margin call? O a. $17.50. b. $16.45. O C. $15.38. d. $10.52. e. None of the above