Battech manufactures generators and alternators, both require wiring and testing during assembly. Each generator requires 2 hours of wiring and 1 hour of testing and are sold for a $250 profit. Each alternator requires 3 hours of wiring and 2 hours of testing and are sold for a $150 profit. There are 260 hours of wiring time and 140 hours of testing time available in the next production period and Electrotech wants to maximize profit. There are three constraints to the model. Which constraint is missing?

• 2 X1 + 3 X2 260
• 1 X1 + 2 X2 140

a. X1, X2 0

b. X1, X2 > 0

c. X1, X2 = 0

d. X1, X2 0