Consider a bullish spread option strategy using a call option with a $52 exercise price priced at $4.80 and a call option with a $64 exercise price priced at $2.72.

a. If the price of the stock increases to $60 at expiration, what is the net profit per share at expiration (ignoring transaction costs)?

b. If the price of the stock increases to $68 at expiration, what is the net profit per share at expiration (ignoring transaction costs)?