X1 X2 X3 X4 Y X3, X4 0 0 0 0 00 01 11 0 0 0 1 X1, X2 00 0 0 1 0 01 0 0 1 1 11 0 1 0 0 10 0 1 0 1 0 1 1 0 0 1 1 1 1 0 0 0 1 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 1 1 1 1 10