Mathematics

Problem

Which of the following statements is both necessary and sufficient for two functions

f:A\to B

and

g:B\to A

to be mutual inverses? a)

f\circ g=I_{B}

only b) Both

f

and

g

are one–one c)

f\circ g=I_{B}

and

g\circ f=I_{A}

d) Both

f

and

g

are onto