Feedback?

EXERCISE

$6\mathrm{.}17\mathrm{.}30$: $($Problem $5\mathrm{.}30$ in the $9$th edition$).$

A reversible refrigeration cycle operates between cold and hot reservoirs at temperatures $T_C$ and $T_H,$ respectively.

If the coefficient of performance is $3\mathrm{.}5$ and $T_C=-40F,$ determine $T_H,$ in $F.$

$($b$)$ If $T_C=-30C$ and $T_H=-30C,$ determine the coefficient of performance.

$($c$)$ If $Q_C=500$Btu,$Q_H=800$Btu, and $T_C=-30F,$ determine $T_H.$ in $F.$

$($d$)$ If $T_C=-30F,$ and $T_H=-100F,$ determine the coefficient of performance.

$($e$)$ If the coefficient of performance is $8\mathrm{.}9$ and $T_C=-5C,$ find $T_H,$ in $C.$