(a) A person is justified in the use of force against another when and to the extent it appears to such person and such person reasonably believes that such use of force is necessary to defend such person or a third person against such other’s imminent use of unlawful force.

(b) A person is justified in the use of deadly force under circumstances described in subsection (a) if such person reasonably believes that such use of deadly force is necessary to prevent imminent death or great bodily harm to such person or a third person.

(c) Nothing in this section shall require a person to retreat if such person is using force to protect such person or a third person.