Suppose the initial margin m_0 = 50% and the maintenance margin m_1 = 30%. The current stock price is $75 per share, and you sell short 1000 shares of the stock now. If you want to keep your short position after the third margin call, how much cash do you need in advance at least? Simply compute the sum of the initial margin amount, 1^st extra margin, 2^nd extra margin, and 3^rd extra margin all together without time discount. Type your answer without $ and round it to the nearest dollar. For example, if your answer is $345, 284.23, then type 345284.