Let 1, V, 0, and denote the AND, OR, Exclusive-OR, and NOT operators, respectively. Consider X1, X2, ..., Xn, y {0,1}. A Boolean function f is called a self-dual function if f(x1,x2,...,xn) = f(X1, X2, ..., In). Answer the following questions. n-1 (4) Prove that the total number of n-variable self-dual functions is 22