Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100 C and the inside heat transfer co-efficient is 3k/l. If the wall temperature on the outside is held at 25 C, what is the inside wall temperature in degree centigrade ?

• A. 35.5
• B. 43.75
• C. 81.25
• D. 48.25