A 50-cm thick wall consists of 20 cm of aluminum, followed by 10 cm of silver, followed by 5 cm of copper followed by 15 cm of iron. If the area of the wall is 5 m by 4 m wall, compute the rate of heat flow through this wall if its left end is at 0oC and its right end is at 100oC.
(a) 637.8 kW
(b) 647.8 kW
(c) 657.8 kW
(d) 667.8 kW
(e) 677.8 kW
(f) None of the above.