a) Displacement is given by the minimum distance between the initial and final positions of a body. In the given case, the cyclist comes to the starting point after cycling for 10 minutes. Hence, his net displacement is zero.
b) Average velocity is given by the relation:
Average velocity = Net displacement/Total time
Total path length = OP + PQ + QO = 1 + 1/4(2π x 1) + 1
= 2 + (1/2)π = 3.570
Time taken = 10 min = 10/60 = 1/6 h
Average speed = 3.570/(1/6) = 21.42 km/h