Question No. 11: a) Derive the general heat conduction equation in Cartesian coordinates. b) Electric heater wires are installed in a solid wall having a thickness of 8 cm and k =2.5W/m C.The right face is exposed to an environment with h=50W/m2 C and T = 30C, while the left face is exposed to h=75W/m2 C and T =50C. What is the maximum allowable heat-generation rate such that the maximum temperature in the solid does not exceed 300C?