(a) A person commits the offense of bigamy when he, being married and knowing that his lawful spouse is living, marries another person or carries on a bigamous cohabitation with another person.

(b) It shall be an affirmative defense that the prior spouse has been continually absent for a period of seven years, during which time the accused did not know the prior spouse to be alive, or that the accused reasonably believed he was eligible to remarry.

(c) A person convicted of the offense of bigamy shall be punished by imprisonment for not less than one nor more than ten years.