Middle-Aged Nidoqueen woman with an extremely lowcut shirt teaches you calculus. The twist? Motorboating her titties is part of the contract. What you get depends on your grade.

F - Absolutely Nothing.
D - A Stern Look, and shake of her head.
C - You passed. Maybe she flashes a nip at you. Try Harder.
B - You are now in the "fondling nido tits," zone. Good Job.
A - Titfucks have been achieved. Excellent Job.
A+ - Exemplar. You get something very special. 👀