Olivia decides to set up an ice cream stand on a hot summer day.Before long, Olivia's friends all decide they would like to help.The table below shows what happens to the number of cups ofice cream Olivia and her friends can make in an hour.

Labor (workers)	Total Product
0	0
1 (Olivia)	15
2	24
3	30
4	34
5	31

Suppose that Olivia was making ice cream alongside two friends and decides to invite an additional friend to help. How many additional cups of ice cream can Olivia produce if she has three friends help her rather than having two friends help her?

4

6

9

-3

explain