Let A={x 1, x2, ..., xn}, then the sum of products of subset elements is (x1+1) (x2+1) * ... * (xn+1)-60.

Induction can prove it. Here is a simple proof:

Let f (a) = the product of elements of a, and the sum of the product of elements of a subset of g (a) = a.

Then the subset of A {x_(n+ 1)} is divided into two types: X and X {x_(n+ 1)}, where X is a subset of A. If X is not empty, then f(X and {x _ (n+1)}). If x is empty, then f (x and {x _ (n+ 1)}) = x _ So g(A and {x _ (n+1)}) = x _ (n+1)+g (a)+x.