Continuing on . . . It looks like the first lady in this clip decides to settle for an A- as she seems like she is just a bit too uncomfortable to complete her task.
Don't feel bad for Tomas, though . . . there are plenty of other students out there who are seeking to bump (and grind) up their grades.
Again, this clip comes with a caution; the first chick looks like an anal virgin and is uncomfortable (not necessarily with her decision, but definitely with Tomas' dick up her ass).