(1) If the expense accounts contain charges or credits from associated companies or nonutility departments of the utility, submit for each such associated company or nonutility department work papers showing the following:

(a) The amount of the charges or credits during the test period;

(b) The account classification or classifications charged or credited;

(c) Descriptions of the specific services performed for or by the associated company or nonutility department;

(d) The basis used in determining the amounts of the charges or credits.