Two solid cylindrical rods AB and BC are welded together at B and loaded as shown. The average normal stress at section F is A1-200mm B A2- 400mm 300 kN 150 kN 100 KN 0.7 m p.2 m 0.6 m 0.4 m Select one: .-750 O b.-125 MPa . 1250 O d. 250 MPa