Answer: b. $9,000
There are 2 alternatives for Jarret company. If it will choose the first, the land will give it a profit of $36,000 per year. If it chooses the second, the profit will be 9% of $300,000 or $27,000.
Opportunity cost is ($36,000-$27,000) or $9,000 which is the loss of potential gain from option 1 when one alternative is chosen.