Pebble-bed nuclear reactor is a design for a graphite-moderated gas-cooled nuclear reactor. The basic fuel design features spherical fuel elements called pebbles. Consider the tennis ballshape fuel elements as a sphere with internal heat generation and constant properties. Heat is generated uniformly at a rate of S per volume. The ball has constant thermal conductivity k and radius R. The ball is exposed to a gas cooling media with a heat transfer coefficient of h. The temperature of the cooling gas media is T0. Find out the temperature distribution in the ball under steady state condition. (Hint: (1) temperature in the ball has to be finite; (2) surface cooling is controlled by convective heat transfer))