(a) A person commits the crime of robbery in the first degree if the person violates AS 11.41.510 and, in the course of violating that section or in immediate flight thereafter, that person or another participant
(1) is armed with a deadly weapon or represents by words or other conduct that either that person or another participant is so armed;
(2) uses or attempts to use a dangerous instrument or a defensive weapon or represents by words or other conduct that either that person or another participant is armed with a dangerous instrument or a defensive weapon; or
(3) causes or attempts to cause serious physical injury to any person.
(b) Robbery in the first degree is a class A felony.