5)     (given)
or
r
h  = 0 5
or
r = 2
h
Let V be the  volume of the cone Then
V =
2
3
2
1
1
3
3
2
12
h
h
r h
h
π


π
=
π
=




Therefore
dV
dt  =
3
12
d
h
dh
dh
dt


π
⋅




(by Chain Rule)
=
2
4
dh
h dt
π
Now rate of change of volume, i e