Question
The radius of the base of a cone is increasing at the rate of 3 cm/minute and the altitude is decreasing at the rate of 4 cm/minute. The rate of change of lateral surface when the radius = 7 cm and altitude 24 cm is
(a) 54π cm2/min
(b) 7π cm2/min
(c) 27 cm2/min
(d) none of these