Holly Consumes Commodities X and Y and Her Utility Function

Holly consumes commodities x and y and her utility function is U(x, y) = xy⁵. Good x costs $2 per unit and good y costs $1 per unit. If she is endowed with 7 units of x and 4 units of y, how many units of good y will she consume?

A) 7
B) 15
C) 19
D) 18
E) None of the above.