Answer
$2,640,000\ ft\cdot lb$
Work Step by Step
If a constant force ${\bf F}$ acts through a displacement
${\bf D}=\vec{PQ}$
the work done is ${\bf W}={\bf F}\cdot{\bf D}$
---
${\bf F}\cdot{\bf D}=|{\bf F}|\cdot|{\bf D}|\cos\alpha,\quad 1\ mi=5280\ ft.$
${\bf W}=(1000\ lb)(5280\ ft)(\cos 60^{\circ})$
$=5,280,000\displaystyle \cdot\frac{1}{2}\ ft\cdot lb$
$=2,640,000\ ft\cdot lb$
