Whenever the authority shall deem it necessary, in order to carry out its obligations under the Power Authority Act and the authority's contracts for the sale of power for resale, to investigate the failure of any customer of the authority to comply with the provisions of its contract governing the resale of power and energy or failure to comply with any request of the authority made pursuant to such provisions, or to investigate the operations, service, practices, accounting records, rates, charges, rules and regulations, or to make valuations or revaluations of property of any such customer of the authority, such customer shall be charged with and pay such portion of the compensation and expenses of any member, officer, agent, consultant or employee of the authority, including any agent, consultant or employee temporarily engaged by the authority, as is reasonably attributable to such investigation, valuation or revaluation. The authority shall ascertain the costs, including the compensation and expenses of any member, officer, agent, consultant or employee, and shall determine the amount to be paid by the customer and a bill shall be rendered therefor by the authority to the customer. The amount of any such bill so rendered shall be paid to the authority by such customer within 30 days from the date of its rendition unless, within such period, the customer so billed shall request an opportunity to be heard as to the amount thereof. If such a request is made, the authority shall designate a member of the authority or a member of the staff to conduct a hearing and report to the authority. The authority shall reconsider the charges and advise the customer of its determination. The bill as finally rendered shall be paid within 30 days after the date of service of such determination.