In connection with surveillance of emissions from new vehicles prior to their retail sale, the manufacturers of such vehicles shall pay fees to permit the state board to recover the state board's direct and indirect costs in conducting such surveillance. These costs will be computed on a person-hour basis according to time spent on each manufacturer, and shall include personnel salaries, administrative overhead, travel time and expenses. With respect to surveillance conducted away from the state board's Vehicle Testing Laboratory, if more than one manufacturer is involved in a particular trip, travel time and expenses shall be apportioned among them according to time spent in surveillance of each manufacturer's vehicles. The computations used in establishing fees will periodically be revised and shall be available upon request.