Unexpended balances of any money which is collected to carry out the educational and trade stimulation efforts which are provided for in Sections 59816, 59817, and 59818 which are sufficient in amount to warrant incurring the expense of making a refund shall be refunded following the termination of any marketing program which contains provisions which are authorized by those sections or following the suspension or termination of educational and trade stimulation provisions of any marketing program. The refund shall be made upon such pro rata basis as the program committee and the director determine is equitable.