Bill Cosby is offering a reward in the case of a suburban New York black teen-ager who was kidnaped and sexually assaulted by six white men. Cosby and Ed Lewis, publisher of Essence, are offering $25,000 for information on the attackers of Tawana Brawley, 16, who was raped last November by the men who wrote racist epithets on her body and left her for dead. "Let Miss Brawley represent an example of what we are not going to stand for as parents, as Americans, as human beings. It's not about race," Cosby said at a news conference in New York. He called the attack "a terrible, terrible thing."