Let M be the number of units to make and B be the number of units to buy.

. Let M be the number of units to make and B be the number of units to buy. If it costs $2 to make a unit and $3 to buy a unit and 4000 units are needed, the objective function is

A. Max 2M + 3B
B. Min 4000 (M + B)
C, Max 8000M + 12000B
D. Min 2M + 3B