(a) Except as provided by subsection (b) of this section, if criminality of conduct in this article depends on a victim being under sixteen (16) years of age, it is an affirmative defense that the actor reasonably believed that the victim was sixteen (16) years of age or older.
(b) If criminality of conduct in this article depends upon a victim being under twelve (12) years or under fourteen (14) years, it is no defense that the actor did not know the victim's age, or that he reasonably believed that the victim was twelve (12) years or fourteen (14) years of age or older, as applicable.