问题如下：
The current market price of PZ company is $35. Tim, a trader of an investment company, has decided to sell short 350 shares of PZ company, because he believes the stock price will go down in the coming future. The initial margin requirement is 60%. Which of the following statements regarding the margin requirement that Tim is subject to on this short sale is correct?
选项：
A.Tim will need to contribute $7,350 ?as margin.
B.Tim will need to contribute $5,640 as margin.
C.Tim dose not need to contribute any additional funds and will only need to leave the short sale's proceeds as deposit.
解释：
A is correct.
The cash from the short sale is $35×350=$12,250
Tim will need to contribute $7,350 (60%× $12,250 =$ 7,350 )as margin.
请问老师0.6x12250=7350. 这里的60% initial margin requirement和12250的关系是什么，为什么拿initial margin requirement去乘以总共的shares价格12250呢？不好意思 数学真的完全忘记了，问了超级多问题给老师添麻烦了
