Corts's logic is best demonstrated through a simple example.Suppose there are two types
of cerael a buyers, students and professors,and two types of cereal,Kellogg's Raisin Bran and
General Mills Cheerios. At equal prices students prefer Cheerios, but professors prefer Raisin
Bran.Assume that both cereals are manufactured at zero marginal cost.Al so suppose that students
cut coupons and professors do not. Without coupons( i.e.,if the sellers are constrained to charge
uniform prices),there is a plausible set of assumptions under which the Cheerios price would
be lower than the optimal price to students and higher than the optimal price to professors,
and the uniform Raisin Bran price would be higher than a student-only price and lower than a
professor-only price.