The graph of the function
is
- concave upward, when

- concave downward, when

Find 
1.

2.

Now:
1. when
the graph of the function is concave upward and this is for

2. when
the graph of the function is concave downward and this is for

Negative 4 is less than negative 1
Using this formula, the gross profit percentage is approx. 75%
It would be 45 cups because each number is multiplied by 5
2 x 5 = 10
3 x 5 = 15
4 x 5 = 20
9 x 5 = 45