ANSWER:
4242.64 lbs*ft
Explanation:
To better understand we make a sketch of the situation:
Where,
Distance ||PQ|| = 100 ft
Force (F) = 60 lbs
The angle between force and displacement is 45°
Component of force along displacement is F * Cos 45°
The total work is calculated by means of the formula shown in the statement:

The total work is equal to 4242.64 lbs*ft