What Do You Recommend Sir?

Joanna is looking through your books and wants to know what you recommend for her revision, you are far too sidetracked though by her big tits to give her an answer. It doesn't take Joanna long to realise what you are doing and she comes up with an idea, she has been struggling with her revision lately so if you agree to give her good grades no matter what she will let you take your cock out and have a wank right now while she teases you.