Snowball Rolling down a hill problem.

Hi all,

I've just started taking differential equations and I've gotten a little bit stuck on this problem.

A snowball rolling down a hill gains mass, m , at a rate proportional to its surface area.Assume the density of the snowball is constant such that mass is proportial to volume. Find a DE for the change in mass over time. And also given is that the rhs should depend only on m and constants

*So here's what I think,*

*Surface= $\displaystyle 4Pi^2$*

*Volume=$\displaystyle 4/3Pi^3$*

*dm/dt=m0 + k*4pi^2*

*Maybe something like the rate of change of the mass depends on the initial mass + the change proportinal to its surface area? *