Answer: 50 baseballs
Step-by-step explanation: Opportunity cost is the cost if the next best alternative foregone. Per unit opportunity cost is calculated by dividing the number of units lost by the number of units gained of a good.
Katie can produce 25 baseballs or 15 bats in a month. So, her opportunity cost of producing 30 bats will be 50 baseballs.
25 baseballs = 15 bats
50 baseballs = 30 bats