When Burning Bob's Salsa House Hires One Worker, 30 Customers

Multiple Choice

When Burning Bob's Salsa House hires one worker, 30 customers can be served in an hour. When Burning Bob's Salsa House hires two workers, 50 customers can be served in an hour. The marginal product of the second worker is ________ customers served per hour.

A) 20
B) 30
C) 50
D) 67.5