Solve 6th sum nd plz tell how is any mapping done.like what is the rule for this mapping

A = {1, 2, 3, 4}

B = {2, 5, 6, 7}

f : A → B mapping from A to B 

f ={(2, 5), (3, 6), (4, 7)}

f is an injective mapping.

As for every element a  A there is an unique element b  B

We define a mapping g:A→B given by g = {(2, 2)(2, 5)(3, 6)(4, 7)}

g is not an injective mapping. As the element 2  A is not uniquely mapped

Since (2, 2) and (2, 5) both belong to the mapping g, g is not injective.

Define a mapping h : A →B given by h = {(2, 2), (5, 3), (7, 4)}

h is a mapping from B to A since the every ordered puts {2, 5, 7}  B to elements in {2, 3, 4}  A