An Overhead Garage Door Has Two Springs,one on Each Side $20$

Multiple Choice

An overhead garage door has two springs,one on each side of the door (see figure) .A force of $20$ pounds is required to stretch each spring 1 foot.Because of a pulley system,the springs stretch only one-half the distance the door travels.The door moves a total of $x = 18$ feet,and the springs are at their natural length when the door is open.Find the combined lifting force applied to the door by the springs when the door is closed.​ ​

A) $$\text { Combined lifting force } = 2 F = 356 \mathrm { lb }$$
B) $\text { Combined lifting force } = 2 F = 360 \mathrm { lb }$
C) $\text { Combined lifting force } = 2 F = 362 \mathrm { lb }$
D) $\text { Combined lifting force } = 2 F = 358 \mathrm { lb }$
E) $\text { Combined lifting force } = 2 F = 364 \mathrm { lb }$