Suppose Eva decides to plant the tulips. Which result would be a cost?
A: She will save some space. The tulips will use up less space than the hickory tree would have used up.
B: Eva will give up the chance to look at the hickory tree. She thinks it would have looked more beautiful than the tulips.
This result is a cost. It involves giving up or spending something that Eva wants or needs:
Eva will give up the chance to look at the hickory tree. She thinks it would have looked more beautiful than the tulips.