How do you beat and make the S go away on Biker Salesman on GTA: Liberty City Stories?

I try to beat it by selling 40 bikes (ten of each) in the avenging angels outfit or whatever, and after i get 40 it doesn't say i've ped it? Then the S is still there like I haven't beat the mission and I don't think I can go on to another mission/island until I beat. Help?