A Force of 20 Pounds Stretches a Spring $\frac { 3 } { 4 }$

A force of 20 pounds stretches a spring $\frac { 3 } { 4 }$ foot beyond its natural length. Find the work done in stretching the spring 1 foot.

A) 20 ft-lb
B) $\frac { 20 } { 3 }$ ft-lb
C) $\frac { 80 } { 3 }$ ft-lb
D) $\frac { 40 } { 3 }$ ft-lb
E) $\frac { 40 } { 9 }$ ft-lb
F) $\frac { 80 } { 9 }$ ft-lb
G) $\frac { 40 } { 6 }$ ft-lb
H) $\frac { 80 } { 6 }$ ft-lb