(a) Separate common debit expense accounts in proportion to the separation of solely related (freight or passenger service) in each individual account. If there are no solely related expenses or if the solely related expenses are assignable entirely to freight or passenger service, separate common debit expense accounts on the same percentages calculated for the separation of administration (account XX-27-01).
(b) Separate common credit expense accounts on the basis of the same percentages calculated for the separation of administration (account XX-27-01).