Each utility shall so keep the records supporting the entries to each steam operating revenue account that it can furnish, (a) the name of each customer, (b) the quantity of steam furnished to each customer, (c) the amount charged for steam furnished each customer and (d) the service classification under which the charge is made. Each utility shall also be prepared to report upon request, within a reasonable time, for each month or other billing period and for each year, the quantity of steam sold and the charges therefor, by service classifications.