A spherical snowball is melting in such a way that its radius is decreasing at a rate

Question

A spherical snowball is melting in such a way that its radius is decreasing at a rate of 0.1 cm/min. At what rate is the volume of the snowball decreasing when the radius is 10 cm. (Note the answer is a positive number).

Answer 1

V = (4/3)pi * R^3

dV/dt = 4*pi * R^2 dR/dt

= 4*pi*10^2 * -0.1

+or-125.66370614359172953850573533118

I disagree, the volume and the radius are decreasing

functions of time. Their slopes MUST be negative