The annual appropriation act to the university for general maintenance may specify the purposes or areas for which such appropriations may be expended by the university. The annual appropriation act may also contain a tuition supplement requiring the university to maintain such tuition and fee schedules for Pennsylvania resident full-time students as set forth annually in such appropriation act: Provided, That the amounts appropriated by the act are sufficient for the maintenance of such schedules by the university: And, provided further, That for any given year, in the event the amounts appropriated are not sufficient for the maintenance of the tuition and fee schedules, the university shall have the right to alter the schedules to the extent necessary to provide required income equal to the amount not provided by the appropriation act.