A bolt in a pressure vessel is tightened with a preload of 7000 N. The external load on the bolt varies from 0 to 9000 N. The constant based on stiffnesses of bolt and member is 0.33. Yield strength is 260 MPa. Endurance limit in reversed axial loading is 130 MPa. Stress concentration factor is 2.8. Factor of safety is 3.0. Stress area of the bolt based on Soderberg's criterion is (a) 195 mm 2 (b) 240 mm (d) 327 mm 2 (c) 285 mm