b. 1.
Step-by-step explanation
Having a mechanical advantage means the force applied by the system is greater than the force you put in. In a pulley system, this means the pulley can lift the object with a greater amount of force than you apply to the rope
The mechanical advantage of a pulley is system is equal to the number of ropes supporting a movable pulley
hence, the force advantage is equal to the number of ropes
therefore
we can see the input force equals the output, so
![\begin{gathered} force\text{ advantage=}\frac{output\text{ force}}{input\text{ force}} \\ force\text{ advantage=}\frac{50\text{ N}}{50\text{ N}} \\ force\text{ advantage=1} \end{gathered}]()
therefore, the answer is
b. 1.
I hope this helps you