Aspherical snowball is melting at the rate of 2 cubic inches per minute (and it's staying spherical). how fast is the radius of the snowball decreasing when the radius is one-half inch?

Volume of Sphere V = (4/3)πr³

Given  dV/dt = 2 in³/minute,    r = 1/2 = 0.5 inch

dV/dt =  dV/dr    *    dr/dt

V = (4/3)πr³

dV/dr =  3*(4/3)πr³ ⁻ ¹ = 4πr² = 4π*0.5² = 4π*0.25 = π   in²

dV/dt =  dV/dr    *    dr/dt

2 in³/minute  =   π  * (dr/dt)

π in²  * (dr/dt)  = 2 in³/minute 

(dr/dt) =  (2 in³/minute) / (π in²)

(dr/dt) = (2/π) in/minute.

The radius of the snowball is reducing at  (2/π)  inches/minute.  

I’m pretty sure the answer is a