How much to fix broken speedometer? on 1993 Nissan Altima

My speedometer is broken, it falls past the 110 mph area and stays, until I get on the freeway and it goes to about 80mph, but every once and a while it will work but then stop and fall back down? What could be the problem and how much would it cost to fix it?

Asked by for the 1993 Nissan Altima
Good luck nobody knows the fix