Related Rates - Oil Spillage

An oil spillage on the surface of the sea remains circular at all times. The area of the spillage remains to be A 𝑘𝑚2 & increases at a rate of 0.5 𝑘𝑚2ℎ−1. Calculate the rate in which the radius r of the spillage is increasing when the area of the spill has reached 10𝑘𝑚2.