A $10cm$ diameter steam pipe, carrying steam at $180C,$ is covered with an insulation $($thermal conductivity $*0\mathrm{.}6\frac{W}{m}K)$ of thickness of $2cm.$ It loses heat to the surroundings at $30C.$ Assume a heat$-$ transfer coeffieient of $8\frac{W}{m^2}K$ for heat transfer fror. surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. The surface temperature of the insulation exposed to the surroundings will be

$($a$)30C$