The length x of a rectangle is increasing at the rate of 2 cm/minute and the width y is decreasing at the rate of 2cm/minute. When x =10cm and y = 10 cm, find the rates of change of the perimeter of the rectangle.

The perimeter increases at the rate of 8 cm/m The perimeter decreases at the rate of 8 cm/s The perimeter changes at the rate of 0 cm/m None of these

The perimeter changes at the rate of 0 cm/m

dP/dt = 2(dx/dt +dy/dt)