What is the ratio of the permissible bearing stress in power driven shop rivets relative to the yield stress of mild steel ?

ANS:B - 0.8

The question is from wsm as rivet is mentioned. Now design stress in axial tension = 0.6fy and in design bearing stress = 0.75fy.

Now for bolts/rivet, fy is not defined n we take fu which is approx 400 . Hence yield stress for for rivet = 0.6 * 400 = 240.
In bearing stress 0.75fy.
Hence, 0.6/0.75 = 0.8.