$70(8)$ A $50-m-$long section of a steam pipe whose outer at $1C$ diameter is $10$ cm passes through an open space pipe is efficient termine $($a$)$ the outer surface of the pipe is $20\frac{W}{m^2}*C,$ deannual cost of this energy lost if steam is generated in a natural gas furnace that has an efficiency of $75.$percent and the price of natural gas is $$\frac{0\mathrm{.}52}{?}$ therm $(1$ therm $=105\mathrm{.}5(**)kJ),$ and $($c$)$ the thickness of fiberglass insulation $(k=0\mathrm{.}035\frac{W}{m}*C)$ needed in order to save $90$ percent of the heat lost. Assume the pipe temperature to remain constant at $150C.$