The 'normal freight rate' shall be determined taking into account: (i) the comparable rate actually charged in the ordinary course of shipping business for the like service on the same or comparable route by established and representative companies not enjoying the advantages in (b); (ii) or otherwise the constructed rate which is determined by taking the costs of comparable companies not enjoying the advantages in (b) plus a reasonable margin of profit. This cost shall be computed on the basis of all costs incurred in the ordinary course of shipping business, both fixed and variable, plus a reasonable amount for overhead expenses.