Copper wire with a diameter of 0.5 cm is covered with  0.65-cm layer of insulating material having a thermal conductivity of 0.242 W/m · K. The air adjacent to the insulation is at 290 K. If the wire carries a current of 400 A, determine
a. The convective heat-transfer coefficient between the insulation surface and the surrounding air
b. The temperatures at the insulation-copper interface and at the outside surface of the insulation