Consider a bullish spread option strategy of buying one call option with a $30 strike price at a premium of $3 and writing a call option with a $40 strike price at a premium of $1.50. If the price of the stock increases to $42 at expiration and the option is exercised on the expiration date, the net profit per share at expiration will be _____ A) $8.50 B) $9.00 C) $9.50 D) $12.50