Two upright plane mirrors touch along one edge, where their planes make an angle of . A

Two upright plane mirrors touch along one edge, where their planes make an angle of α. A beam of light is directed onto one of the mirrors at an angle of incidence of β(β < α) and is reflected onto the other mirror.
(a) Will the angle of reflection of the beam from the second mirror be (1) α, (2) β, (3) α + β, or (4) α – β?
(b) If α = 60o and, β = 40o,what will be the angle of reflection of the beam from the second mirror?