How do u get an A ranking on resident evil code: veronica on battle game for all characters on ps2?

OK, so i've already gotten an A for Wesker and Steve, but when i beat Claire's battle game in under 7 minutes, i get a B. WTF?! I cant get an A for Claire's alternate costume or chris, either. Plz help me out so i can get the linear launcher for Resident Evil Code: Veronica. thanks.