This is the problem I am having...

All edges of a cube are expanding at a rate of 3 centimeters per second. How fast is the volume changing when each edge is

(a) 1 centimeter

(b) 30 centimeters

The equation I am using is

V = S³

This is what I did

dv/dt = 3s² ds/dt

dv/dt = 3 (1)² x 3

dv/dt = 3 x 3

dv/dt = 9

dv/dt = 3s² ds/dt

dv/dt = 3 (30)² x 3

dv/dt = 3 (900) x 3

dv/dt = 2700 x 3

dv/dt = 8100

I am just wondering wheter or not I did this equation right so I can look back over it and find the mistake.