Suppose Celine decides to plant the lilies. Which result would be a cost?
She will save some space. The lilies will use up less space than the oak tree would have used up. Celine will give up the chance to look at the oak tree. She thinks it would have looked more beautiful than the lilies.
Celine is deciding whether to plant lilies or an oak tree in her backyard. She wants to make her backyard more beautiful. But she also wants to leave space for doing fun things.
Before you decide to do something, it is often helpful to list costs and benefits.
Costs are what you give up or spend when you decide to do something. Costs involve giving up things that you want or need.
Benefits are what you gain or save when you decide to do something. Benefits involve gaining something that you want or need.
This result is a cost. It involves giving up or spending something that Celine wants or needs:
Celine will give up the chance to look at the oak tree. She thinks it would have looked more beautiful than the lilies.