Answer:
5.0 ft-lbf
Step-by-step explanation:
The force is

This force is not a constant force. For a non-constant force, the work done, <em>W</em>, is

with
and
the initial and final displacements respectively.
From the question,
and
.
Then

Evaluating the indefinite integral,

From the rules of integration,


Returning the limits,

Answer:
81/20
Step-by-step explanation: