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(Total is 2^n)
A set with n elements has 2^n total subsets, including the empty set and the full set.
Proof: sum C(n,0) + C(n,1) + ... + C(n,n) = 2^n. This follows from the binomial theorem with a=1, b=1: (1+1)^n = 2^n.
Example: a set {A,B,C} has 2^3 = 8 subsets: {}, {A}, {B}, {C}, {A,B}, {A,C}, {B,C}, {A,B,C}.
