(6) Consider a 20 ? cm -thick large concrete plane wall ( k = 0.77 W / m ? K ) subjected to convection on both sides with T ?1 ? = 2 7 ? C and h 1 ? = 5 W / m 2 ? K on the inside, and T ?2 ? = 8 ? C and h 2 ? = 12 W / m 2 ? K on the outside. Assuming constant thermal conductivity with no heat generation and negligible radiation, ( a ) express the differential equation and the boundary conditions for steady one-dimensional heat conduction through the wall, (b) obtain a relation for the variation of temperature in the wall by solving the differential equation, and ( c ) evaluate the temperatures at the inner and outer surfaces of the wall