The width of a rectangle is increasing at a rate of 5 inches per second and its length is increasing at the rate of 2 inches per second. At what rate is the area of the rectangle increasing when its width is 3 inches and its length is 6 inches? [Hint: Let W(t) and L(t) be the width and length, respectively, at time t]

The rate that the area of the rectangle is increasing is ____ in² /s (simplify your answer)