Consider a solid cylindrical rod of length 0.15 m and diameter 0.05 m. The top and bottom surfaces of the rod are maintained at constant temperatures of 20°C and 95°C, respectively, while the side surface is perfectly insulated. Determine the rate of heat transfer through the rod if it is made of

(a) Copper, k = 380 W/m·K,

(b) Steel, k = 18 W/m·K,

(c) Granite, k = 1.2 W/m·K.