单项选择题

An investor buys a call option with a $25 exercise price priced at $4 and writes a call option with a $40 exercise price priced at $2.50. If the Price of the stock increases to $50 at expiration and the options are exercised on the expiration date, the net profit at expiration (ignoring transaction costs) is:

A.<TABLE border=0 cellSpacing=0 cellPadding=0 width="90%"><TBODY><TR><TD vAlign=top>A. $8.50. </TD></TR></TBODY></TABLE>
B.<TABLE border=0 cellSpacing=0 cellPadding=0 width="90%"><TBODY><TR><TD vAlign=top>B. $13.50. </TD></TR></TBODY></TABLE>
C.<TABLE border=0 cellSpacing=0 cellPadding=0 width="90%"><TBODY><TR><TD vAlign=top>C. $16.50.</TD></TR></TBODY></TABLE>