b := (not b and not a) or (b and a) or (not b and not x) or (not x)
a := b and x
y := (not b and not a) or (b and a and not x)
b a x b a y
0 0 0 0 1 0 1
1 0 0 1 1 0 1
2 0 1 0 1 0 0
3 0 1 1 0 0 0
4 1 0 0 1 0 0
5 1 0 1 0 1 0
6 1 1 0 1 0 1
7 1 1 1 1 1 0