4.
Peter wishes to make a cone to hold water. He makes a
right circular cone, without overlap, of depth h cm, radius
r cm and slant height 12 cm.
Show that the volume of the cone, V cm³ is given by V =
48 π h-1/3π h³. Find the value of h for which V has a stationary value. Find this value of V and determine whether it is a maximum or minimum.