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 Total Revenue Total Costs 10 $ 2,600 $ 1,800 15 3,600 2,300 16 3,800 2,470 20 4,600 3,270 21 4,800 3,360 The marginal cost when the twenty-first student enrolls in the school is:

• $90.

• $142.

• $200.

• $3,180.

• $3,360.