Answer
$\mathrm{COP}_{\mathrm{R}}=13.7\text{ Btu/min}$
Work Step by Step
The required power input is determined from the definition of $\mathrm{COP}_{\mathrm{R}}$,
$$
\mathrm{COP}_{\mathrm{R}}=\frac{\dot{Q}_L}{\dot{W}_{\text {in }}} \longrightarrow \dot{Q}_L=\mathrm{COP}_{\mathrm{R}} \dot{W}_{\text {in }}=(0.18)(1.8 \mathrm{hp})\left(\frac{42.41 \mathrm{Btu} / \mathrm{min}}{1 \mathrm{hp}}\right)=13.7\ \mathrm{Btu} / \mathrm{min}
$$
