A Campaign Manager for a Political Candidate Must Arrange the Shipment

Multiple Choice

A campaign manager for a political candidate must arrange the shipment of 150 cartons of campaign buttons from three button producers to three campaign headquarters. The supplies and demands, and the per-carton transportation costs, are shown below:
Which of the following is a constraint for the customer (campaign headquarters) ?

A)  2X11 + 9X21 + X31 = 20
B)  5X12 + 3X22 + 8X32 = 70
C)  X11 + X12 + X13 = 50
D)  X12 + X22 + X32 = 70
E)  all of the choices