Consider a plane composite wall that is composed of two materials of thermal conductivities ka = 0.1 w/m*k and kb = 0.04 w/m*k and thicknesses la = 10 mm and lb = 20 mm. the contact resistance at the interface between the two materials is known to be 0.30 m2*k/w. material a adjoins a fluid at 200°c for which h = 10 w/m2*k, and material b adjoins a fluid at 40°c for which h = 20 w/m2*k. (a) what is the rate of heat transfer thro