Carl purchased a call option on Apex stock that had a premium of $4, an exercise price of $25, and six-months to expiration. When he purchased the option, Apex was selling at $27 per share. What profit (per share) would Carl earn on his option transaction if Apex sells at $31 per share at expiration?

*please solve algebraically*

a) $0

b) $2

c) $4

d) $6