Answer
The work done is 1079 foot-pounds.
Work Step by Step
Here, the box is pulled horizontally, such that the angle between the force and direction of motion is $\left( 38{}^\circ -12{}^\circ \right)$.
Now it is known,
$\mathbf{W}=\left\| \mathbf{F} \right\|\left\| \mathbf{AB} \right\|\cos \theta $ …… (1)
As it is given that,
$\left\| \mathbf{F} \right\|=60,\left\| \mathbf{AB} \right\|=20$ and $\theta =\left( 38-12 \right){}^\circ $ …… (2)
Therefore, use (2) in (1).
So,
$\begin{align}
& \mathbf{W}=\left( 60 \right)\left( 20 \right)\cos \left( 38-12 \right){}^\circ \\
& =\left( 1200 \right)\cos \left( 26{}^\circ \right) \\
& =\left( 1200 \right)\left( 0.898 \right) \\
& \approx 1079
\end{align}$
