composite function involving word problem
please help, i'm not sure if i'm on the right track.
A spherical hailstone grows in a cloud. The hailstone maintains a spherical shape while its radius increases at a rate of 0.2 mm/min.
a) Express the radius, r, in millimeters, of the hailstone, as a function of the time, t, in minutes.
i came up with the answer,
r(t) = 0.2t
but i'm not sure if its right
b) Express the volume, V, in cubic millimeters, of the hailstone, in terms of r.
c) Determine (Vor)(t)
not sure if thats right either?
d) What is the volume of the hailstone 1 h after it begins to form?