(a) All overhead construction costs, such as engineering, supervision, general office salaries and expenses, construction engineering and supervision by others than the service company, law expenses, insurance, injuries and damages, relief and pensions, taxes and interest, must be charged to particular jobs or units on the basis of the amounts of the reasonably applicable overheads.

(b) As far as practicable, the determination of payroll charges includible in construction overheads must be based on the related time card distributions. Where this procedure is impractical, special studies must be made periodically of the time of supervisory employees devoted to construction activities to the end that only the overhead costs that have a definite relation to construction must be capitalized.

(c) The records supporting the entries for overhead construction costs must be kept so as to show the total amount of each overhead for each year, the nature and amount of each overhead expenditure charged to each construction project and to each property account, and the bases of distribution of such costs.