You Spend $150 Every Month Planting Flowers in Your Front

You spend $150 every month planting flowers in your front yard. Your neighbor has told you that she derives $20 a month in enjoyment from being able to look at your beautiful flowers. Which of the following is true?

A) You are spending too much on flowers, because your neighbor derives only $20 worth of benefits.
B) You should refuse to spend anything on flowers unless your neighbor pays you $20 a month.
C) If you took into consideration the benefits your neighbor derived, the efficient level of flower planting would be greater than $150 a month.
D) If you took into consideration the benefits your neighbor derived, the efficient level of flower planting would be less than $150 a month.