The rate of heat flow through a composite wall of three layers of thickness 0.3 m, 0.2 m, 0.15 m, and of corresponding thermal conductivities 1.2, 0.8, and 0.6 kJ / hr-m°C is 1280 kJ / hr. If the surface area normal to the direction of heat flow is 1 sq. meter. and inner surface temperature is 1000°C, then the interface temperature at the end of first layer will be

The rate of heat flow through a composite wall of three layers of thic

1.	The rate of heat flow through a composite wall of three layers of thickness 0.3 m, 0.2 m, 0.15 m, and of corresponding thermal conductivities 1.2, 0.8, and 0.6 kJ / hr-m°C is 1280 kJ / hr. If the surface area normal to the direction of heat flow is 1 sq. meter. and inner surface temperature is 1000°C, then the interface temperature at the end of first layer will be
A.	700°C
B.	680°C
C.	500°C
D.	360°C
Answer» C. 500°C