If an Extra Worker Allows a Child Care Center to Care

If an extra worker allows a child care center to care for an extra nine children a week,the weekly price of child care per child is $200,and the other workers are all paid wages and benefits totaling $500 per week,then the marginal revenue of that additional worker is

A) $4,500 per week.
B) $2,700 per week.
C) $1,800 per week.
D) The answer cannot be determined from the information provided.