A square silicon chip (k = 152 W/m·K) is of width 7 mm on a side and of thickness 3 mm. The chip is mounted in a substrate such that its side and back surfaces are insulated, while the front surface is exposed to a coolant. If 6 W are being dissipated in circuits mounted to the back surface of the chip, what is the steady-state temperature difference between the back and front surfaces?