adventures in teaching principles

I put a parabolic Marginal benefit of a wing schedule up, first rising and then falling. The MC of a wing is horizontal and starts above MB and intersects the latter twice, at 5 and 15 wings, respectively. The area between MC and MB from 0 to 5 wings is clearly less than the area between MB and MC from 5 to 15 wings. OK, class how many wings shall I eat if I want maximize net benefits?

Response: Don't eat the first 5!!