In the figure shown, shaft A, made of AISI 1020 hot-rolled steel, is welded to a fixed support and is subjected to loading by equal and opposite forces F via shaft B. A fatigue stress- concentration factor Kfs of 1.6 is induced in the shaft by the 1/8-in weld fillet. The length of shaft A from the fixed support to the connection at shaft B is 2 ft. The load F cycles from 150 to 500 lbf. For shaft A, find the factor of safety for infinite life using the modified Goodman fatigue failure criterion. in fillet Shaft A 7 -in dia 1 in 1 in Shaft B