If the delegation of discretion to determine whether the case, ton, or man-hour basis is most equitable as a basis of prorating the cost of inspection and laboratory control is held invalid as an unlawful delegation of legislative power, the invalidity shall not affect the validity of the remaining portions of this chapter. The Legislature hereby declares that if it had known that the delegation of the discretion would be declared invalid as an unlawful delegation of legislative power, it would have designated the man-hour basis of proration as the most

equitable basis of proration. In the event of an invalidity, the cost of inspection and laboratory control shall be prorated on the man-hour basis.