A man of mass 60 kg is standing on a body of mass 140 kg which is at rest in still water. The man is initially at 20 m from the shore. He starts walking on the boat for 4 s with constant speed 1.5 m/s towards the shore. The final distance of the man from the shore is:
a. 15.8 m
b. 4.2 m
c. 12.6 m
d. 14.1 m