Tiny Totts Is a Nursery School for Kindergarten Children

Multiple Choice

Tiny Totts is a nursery school for kindergarten children. When there are twenty children enrolled, total revenues and total costs are $6,000 and $3,200, respectively. When there are twenty-one children enrolled, total revenues and total costs are $6,300 and $3,255, respectively. The marginal cost when the twenty-first student enrolls in the school is:

A) $55.
B) $155.
C) $300.
D) $3,045.
E) $3,255.