A circular puddle of liquid is evaporating and, as a result, is slowly shrinking in size. r(t): 12 31-4 units, After t minutes, the radius, r, of the surface of the puddle measures where >0 minutes. The area A of the surface area of the puddle is given by A(r)=ar a) Express the area as a function of time and simplify. b) Find the area of the surface of the puddle at t = 10 minutes using the most efficient method. Give an exact answer expressed in terms of .