A light single-engine general aircraft has a wing area of 15 square meters, a wingspan of 9.7 m, and a maximum gross weight of 1111 kg. The wing adopts NACA 65–415 airfoil, the lift coefficient is 0.1033 per degree, and αL=0 =− 3°. Assume τ = 0.12. If the aircraft cruises at 120 mph at standard sea level at its maximum gross weight. Calculate the geometric angle of attack of the wing in straight and level flight.