The firm initially produced 500 pants and 700 shirts. if the firm decides to increase the number of shirts by 100 units, the opportunity cost will be 100 200 400 500 pants.

The opportunity cost is 100 pants

Step-by-step explanation:

The opportunity cost refers, in economics and other disciplines, as the value or the amount of the best rejected option. It is not influenced by the original values you are given of production in this case.

If the firm produces 100 shirts, and assuming he can only produce shirts or pants at one specific moment, he is rejecting the option or the possibility to make 100 pants, assuming that the firm can produce pants or shirts in the same manner (times cost etc).