UPSC NDA I 2015 Mathematics Solved Paper

Consider a set A with n elements. Similarly consider another set B with m elements. Then ‘AxB’ has a total of ‘mn’ elements. A relation from set A to set B will be a subset of ‘A×B’.
The total number of subsets possible for the set ‘A×B’ is
2n(A×B)
=2mn
In the above question n is 3 and m is 4.
Hence the total number of relations from B to A will be
2n(B×A)
=2(4)(3)
=212
=4096