i need to find solution to this calculus question

Question

A circle is inside a square.

The radius of the circle is increasing at a rate of 1 meter per hour and the sides of the square are increasing at a rate of 2 meters per hour.

When the radius is 4 meters, and the sides are 22 meters, then how fast is the AREA outside the circle but inside the square changing?

The rate of change of the area enclosed between the circle and the square is 

Answer 1

Let r = radius of the circle and s = length of a side of the square

Given: dr/dt = 1 and ds/dt = 2

A = area of the region inside the square and outside the circle = s² - πr²

Find: dA/dt when r = 4 and s = 22

dA/dt = 2s(ds/dt) - 2πr(dr/dt) = 2(22)(2) - 2π(4)(1) = (88 - 8π) m/hr