I guess this is trivial

f = {(1,f(1)), (2,f(2)), ... .... .... , (5,f(5))}

Find f(1), f(2) etc based on the given definition.

Note that any function (or a binary mapping) from S->F is a subset of SxF.

Which makes sense as any mapping is a special kind of pairing where as SxF is a set of all possible pairs.