Wilbur consumes only apples and bananas. He prefers more apples to less, but he gets tired of bananas. If he consumes fewer than 18 bananas per week, he thinks that one banana is a perfect substitute for one apple. But you would have to pay him one apple for each banana beyond 18 that he consumes. The indifference curve that passes through the consumption bundle with 27 apples and 30 bananas also passes through the bundle with A apples and 13 bananas, where A equals: