It is an unfair practice for an insurer, and a prohibited practice for a health care service contractor or a health maintenance organization, to fail to respond promptly to any inquiry from the insurance commissioner relative to the business of insurance. A lack of response within fifteen business days from receipt of an inquiry will be considered untimely. A response must be in writing, unless otherwise indicated in the inquiry. If the inquiry originates from the commissioner's electronic company complaint system, the response must be in writing and submitted using that same system. This rule also applies to any other entity or person subject to the requirements of chapter 48.30 RCW.