A black body which is at a high temperature $T \mathrm{K}$, emitted thermal radiation at the rate of $E \mathrm{Watt} {\mathrm{m}}^{-2}$. The thermal radiation emitted by a body of emissivity equal to $0.5$ at temperature $\frac{T}{4}$ (in $\mathrm{watt}\hspace{0.17em}{\mathrm{m}}^{-2}$) is

Three identical conductors, $P, Q$ and $R$ are symmetrically fixed at point $O$ as shown in figure. The temperature of junction $O$ is

Two cylinders of same diameter and length one of iron and other of silver are placed in close contact as shown. If thermal conductivity of silver is $11$ times than that of iron, then temperature of interface A is approximately