since r=h/2 and V=(hpr^2)/3
V=(ph^3)/12
V(15)=281.25p and since V=10t, t=28.125p
V=(ph^3)/12
dV/dh=(3ph^2)/12=(ph^2)/4 and since V=10t, dV/dt=10
(dh/dV)(dV/dt)=dh/dt=12/(3ph^2)*10
dh/dt=120/(3ph^2) and we want the rate when h=15 so
dh/dt(15)=120/(675p)
dh/dt=0.05658 ft/min