A beam AB simply supported at its ends A and B, 3 m long, carries a uniformly distributed load of 1kN/m over its entire length and concentrated load of 3 kN, at 1 m from A:
If ISJB 150 with $I_{xx} = 300cm^{4}$ is used for the beam, the maximum value of bending stress is
(a) 75 MPa (b) 85 MPa
(c) 125 MPa (d) 250 MPa