The names of the files in this directory are important.

A rule must always be named:
  r_<rule_name>_<lhs|rhs|nac>.od

It is allowed to have more than one NAC. In this case, the NACs must be named:
  r_<rule_name>_nac.od
  r_<rule_name>_nac2.od
  r_<rule_name>_nac3.od
  ...


For the assignment, you can delete the existing rules (they are nonsense) and start fresh.