Play Time is a nursery school for pre-kindergarten children. The school has determined that the following biweekly revenues and costs occur at different levels of enrollment: Number of Students Enrolled 1 15 16 Total Revenue $3,000 4,250 4,500 5,500 5,750 Total Costs $1,700 2,700 2,880 3,630 3,715 20 21 The marginal cost when the twenty-first student enrolls in the school is: Multiple Choice $165 $85 $250 $3,715