In the given figure, In a Δ ABC , ∠B = ∠ C. If AM is the bisector of ∠ BAC and AN ⊥ BC, then ∠ MAN is equal to :

• 1 (∠B + ∠C) 2
• 1 (∠C- ∠B ) 2
• ∠B + ∠C
• 1 (∠B - ∠C) 2