Hello, can you help me solve the sections below?

Section 1 - Natural sciences. When the trees grow, they add circular layers of wood every year within their inner bark: Determine the reason for changing the area (dA/dr) of these concentric circles with respect to the radius. Remember that the area of a circle is calculated with the expression A(r) = r^2

Section 2 - Natural sciences. The amount of liters of water contained in a tank when it begins to empty is expressed by Q(t) = 600 (90 - t)^2 where t is given in minutes. How fast does the water come out at the end of 10 minutes?