The design moment for a R.C. beam of b × h=2 0 0 mm × 600 mm is M= 30 0 k N · m , t he concrete is of grade C30 (α 1 =1.0, f c =1 4.3 N/mm 2 , f t =1. 43 N/mm 2 ) , the steel is of grade HRB 400. (f y =3 6 0N/mm 2 , ξ b =0.518 , a s =65mm, ) . Calculate the area of the longitudinal tensile reinforcement of the beam .