Couple word problems I'm having a little trouble getting.

If a snowball melts so that its surface area decreases at a rate of 1 cm^2/min , find the rate at which the diameter decreases when the diameter is 10cm.

and

Brain weight B as a function of body weight W in fish has been modeled by the power function B = 0.002w^(2/3), where B and W are meased in grams. A model for the body, weight, as a function of body lenght L (measured in centimeters) is w = o.12L^2.53. If over 10 million years, the average length of a certain species of fish evolved from 15cm to 20cm at a constant rate, how fast was this species' brain growing when the average length was 18 cm?

Whew, that problem kicks the heck outta me lol. Thanks for any help