For a bolted assembly with 10 bolts, the stiffness of each bolt is kb=4 Mlbf/in and the stiffness of the members is km=12 Mlbf/in per bolt. The joint is subjected to occasional disassembly for maintenance and should be preloaded accordingly. A fluctuation external load is applied to the entire joint with Pmax=80 kips and Pmin=20 kips. Assume the load is equally distributed to all the bolts. It has been determined to use ½ in-13 UNC grade 8 bolts. Determine the fatigue factor of safety using the Goodman criteria.