Example $7\mathrm{.}5.$ A $\frac{3}{4}-$in$.$ steel pipe is insulated with $2-$cm$-$thick fiberglass insulation. If the inside wall of the pipe is at $150C,$ and the temperature at the outside surface of the insulation is $35C,($a$)$ calculate the temperature at the interface between the pipe and the insulation and $($b$)$ calculate the rate of heat loss for one meter length of pipe.