Interesting probability question

[jay_shark]

Here is a neat question that I haven't figured out yet . I'll think about it some more when I get the chance but here it goes .

Let S =[1,2,3...n} and suppose that A and B and independently likely to be any of the 2^n subsets (including the null set and s itself) of S .

Show that P(A is a subset of B) =(3/4)^n