(1) The letter of an electric, natural gas, or private water utility transmitting a rate schedule or a part thereof to the commission for filing, to supersede, supplement or otherwise change the provisions of a rate schedule required to be on file, shall:
(a) List the documents submitted with the filing;
(b) State the names and addresses of those to whom copies of the rate schedule have been mailed;
(c) Include a brief description of the proposed changes in service or rate and charge;
(d) State the reasons for the proposed changes;
(e) State the estimated number of customers whose cost of service will be affected and annual amounts of either increases or decreases, or both, in cost of service to such customers.
(f) Name an employee of the utility who shall be responsible for answering questions concerning the application, or for referring inquiries to appropriate members of the utility staff.