Correct option is (a) 532.1 r.p.m
For explanation I would say: Given α = 20° ; NA = 500 r.p.m.
Let A, B and C are the driving shaft, intermediate shaft and driven shaft respectively. We know that for the driving shaft (A) and intermediate shaft (B),
Maximum speed of the intermediate shaft,
NB(max) = NA/cosα = 500/cos 20°= 532.1 r.p.m.