The work done by a force can be calculated with the formula below:
[tex]W=F\cdot d[/tex]Where W is the work in Joules, F is the force in Newtons and d is the distance in meters.
So, if an 85 N force is applied over 21 meters, the work done is:
[tex]\begin{gathered} W=85\cdot21 \\ W=1785\text{ J} \end{gathered}[/tex]Therefore the work done by Lee is 1785 J.