A bar made of two solid materials with thermal conductivities KA=10 W/mK and kg=10 W/mK has the cross section shown below. The right side is in contact with an air flow of 20C and h-15 W/mK; the inner surface is in contact with still water of 75C and hw = 35 W/mK; the other surfaces are insulated. Using the finite-difference method with a mesh size of delta_x=delta_y=10 cm, write the steady-state finite-difference equations for the nodes in contact with the air and the equation for the heat flux exchanged with the water, per unit bar length. 30 cm Material A Material 10 cm 20 cm