How do you calculate the effort of a pulley?

The general effort force equation for block and tackle to raise or pull a load can be expressed as

S=F/μn

where
S is the effort force,
F is the load force (often the weight of the object to be moved),
μ is the mechanical efficiency of the system (1 in an ideal, massless, frictionless system of pulleys), and
n is the number of ropes between the sets of pulleys.

it may be wrong but i think its a

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