As volume is cube of the length:
V(e) = e^3
So the rate of change of the volume is or differentiating :
dV/dt = dV/de de/dt = 3e^2 de/dt = 12 e^2 cm/sec
when each edge is 5 cm, dV/dt = 12 25 = 300 cm^3/sec
When each edge is 12cm, dV/dt = 12 * 12^2 = 1728 cm^3/sec
