15.17 The solar radiation incident on a steel plate 2 ft square is 400 Btu/h. The plate is 1.4 in thick and lying horizontally on an insulating surface, its upper surface

being exposed to air at 90 F. If the convective heat-transfer coefficient between the top surface and the surrounding air is 4 Btu/h ft F, what will be the steady-state temperature of the plate?