A slab consists of two parallel layers of copper and brass of the same thickness and having thermal conductivities in the ratio $1 : 4$ . If the free face of brass is at ${100^o}C$ and that of copper at $0^\circ C $, the temperature of interface is ........ $^oC$
  • A$80$
  • B$20$
  • C$60$
  • D$40$
IIT 1981, Medium
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