Related rates help please?

Your neighbor is growing a slightly different watermelon. It also has a rind whose thickness is one tenth of the radius of that watermelon. However, the rind of your neighbor's water melons grows at a constant rate of 20 cubic centimeters a week. The radius of your neighbor's watermelon after 5 weeks is _________ and at that time it is growing at __________ centimeters per week.