DeShawn's Detailing Is a Service That Details Cars at Customers

DeShawn's Detailing is a service that details cars at customers' homes or places of work.DeShawn's cost for a basic detailing package is $40,and he charges $75 for this service.For a total price of $90,DeShawn will also detail the car's engine,a service that adds an additional $20 to the total cost of the package.What is DeShawn's marginal benefit if he sells a basic detailing package?

A) $35
B) $75
C) He incurs a marginal loss of $15, not a marginal benefit.
D) The marginal benefit cannot be determined.