Was wondering if i had the correct formula to plug in different values of r.

The formula for the volume of a cone is given below. Find the rate of change of the volume for each of the radii given below ifdr/dtis 4 inches per minute andh= 15r.

V= (1/3)πr^2h

πr^2(5r)is what i get as the formula but i'm guessing it's probably off, and also needing to know if there is a way to double check your answer if you're unsure of the formula you end up with.