Consider N(A)=m and N(B)=n PB has 112 elements more than PA N(PB)=112+N(PA) N(PB)−N(PA)=112 2n−2m=16×7 Rewrite the above equation. 2m(2n−m−1)=16×7 2m(2n−m−1)=24(23−1) From the above equation, m=4 n−m=3 n−4=3 n=7 The number of injective function from A to B =N(B)PN(A) =7P4 =