Dent 'N' Scratch Used Cars and Trucks Employs 3 Salesmen

Dent 'n' Scratch Used Cars and Trucks employs 3 salesmen.Data for their sales last month are shown in this table: Based on last month's data, Joe's opportunity cost of selling a truck is selling:

A) 9 cars.
B) 1 car.
C) 4 cars.
D) 1/3 of a car.