Let A, B and C be nonempty sets and let f:A→B and g:B→C. ∙ For every a∈A and every b,c∈B, if (a,b)∈f and (a,c)∈f, then \(b = ...Let A, B and C be nonempty sets and let f:A→B and g:B→C. ∙ For every a∈A and every b,c∈B, if (a,b)∈f and (a,c)∈f, then b=c. Then f−1:B→A is a function, and for every a∈A and b∈B, Let f:S→T be a function and let A\(beasubsetof\(S and let C be a subset of T.