Textbook Problem

Nine old 12 ft² windows with $U=1.2\frac{\text{Btu}}{\text{h}\cdot {\text{ft}}^2\cdot °\text{F}}$ were replaced with new windows having $U=0.3\frac{\text{Btu}}{\text{h}\cdot {\text{ft}}^2\cdot °\text{F}}$. Calculate the energy savings on a day during a 5 hour period, when $T_{\text{in}}=68°F$, $T_{\text{outside}}=10°\text{F}$.