A reinforced concrete beam has a width of 300mm and an effective depth of 520 mm. Use fc = 21 MPa and fy = 415 MPa. U = 1.2D + 1.6L. If the beam will carry a total factored moment of 320 kN -m, determine the required number of 25 mm tension bars. Determine the design flexural strength (kN-m) if it is reinforced for tension only by 3-20 mm bars. Determine the design flexural strength (kN-m) if it is reinforced for tension only by 4-28 mm bars.