Rule 1

If e is N and de is N then control is N.

Rule 2

If e is Z and de is N then control is N.

Rule 3

If e is P and de is N then control is Z.

Rule 4

If e is N and de is Z then control is N.

Rule 5

If e is Z and de is Z then control is Z.

Rule 6

If e is P and de is Z then control is P.

Rule 7

If e is N and de is P then control is Z.

Rule 8

If e is Z and de is P then control is P.

Rule 9

If e is P and de is P then control is P.