The ABC company is developing its weekly production plan. The company produces two products, A and B, which are processed in two departments. Setting up each batch of A requires $60 of labor while setting up a batch of B costs $80. Each unit of A generates agross profit of $17 while a unit of B earns a gross profit of $21. The company can sell all the units it produces. The data for the problem is summarized below.

	Hours required by
Operation	A	B	Hours Available
Cutting	3	4	48
Welding	2	1	36

The decision variables are defined as:

X_i= the amount of product i (1= A, 2= B) produced

Y_i= 1 if product i is produced, and 0 if it is not

1. Which of the following constraints is valid?
   1. X1-16Y1<= 0
   2. X1-Y1=0
   3. X1-18Y1>=0
   4. 3X1+4X2=48
2. What is the objective function?