A project manager has four crews that can be hired on a temporary basis during peak construction

Question:

A project manager has four crews that can be hired on a temporary basis during peak construction periods. The manager currently has three projects more than can be handled with his regular crews. It is desired to determine the crew assignments that will minimize the total project cost. The costs of using certain crews for certain projects are presented as follows:

Crew 1 Project A: $\$ 4,000$

Project B: $\$ 3,000$
Project C: $\$ 9,000$
Crew 2 Project A: $\$ 7,000$
Project B: $\$ 1,000$
Project C: $\$ 8,000$
Crew 3 Project A: $\$ 2,000$
Project B: $\$ 6,000$
Project C: $\$ 4,000$
Crew 4 Project A: $\$ 9,000$
Project B: $\$ 5,000$
Project C: $\$ 5,000$