Answer:
W = 8.575 foot-pounds
Step-by-step explanation:
The equation for work is:  W = F*d
where F is force applied and d distance of the movement
from problem statement we have 
d = 0,7 ft
We also know that the spring was stretched 0,4 ft when a force of 7 pounds was applied therefore
K the constant of the spring is
F = K*s      
k = F/s     ⇒   k = 7/0.4         ⇒ k = 17.5  pounds/feet
Now to move from original condition of the spring up to 0,7 feet we need a force of
F = k*s       ⇒  F = 17,5 pounds/feet * 0.7 feet     ⇒ F = 12.25 pounds
And finally the work 
W = 12.25 * 0.7   = 8.575 foot-pounds
W = 8.575 foot-pounds