(a) A person commits the crime of robbery in the first degree if he violates Section 13A-8-43 and he:
(1) Is armed with a deadly weapon or dangerous instrument; or
(2) Causes serious physical injury to another.
(b) Possession then and there of an article used or fashioned in a manner to lead any person who is present reasonably to believe it to be a deadly weapon or dangerous instrument, or any verbal or other representation by the defendant that he is then and there so armed, is prima facie evidence under subsection (a) of this section that he was so armed.
(c) Robbery in the first degree is a Class A felony.