问题如下：
The current market price of PZ company is $30 per share. Tim has $10,000 to invest including cash $5,000 and $5,000 borrowed from a broker. The maintenance margin is 40%. Which of the following statements is correct?
选项：
A.A margin call will first occur at $15.
B.A margin call will first occur at $25.
C.A margin call will first occur at $20.
解释：
B is correct.
Tim's initial equity is $30×0.5=$15
A margin call will occur when the percentage margin drops to 40%.
We use X to replace the stock price when a margin call will first occur.
So we can solve the following equation
The solution is X=$25
请问老师如果这道题假设不是刚好自有资金和借的钱数目相等IM=50%的话，如果是cash6000的话，IM要怎么计算呢是多少除多少，主要是不清楚IM怎么算，谢谢
