An investor entered into a margin purchase transaction. He purchased on margin 100 shares of stock priced at $ 60 per share. The investor borrowed the maximum amount allowed by the initial margin requirement of 50 percent, and the maintenance margin is 30 percent. Under the requirement of margin purchase, the lowest price per share at which the stock could sell before the investor would receive a margin call is closest to:()
A. $30.
B. $40.
C. $43.