The correct answer is (C):
Let the time taken by Partha to cover 60 km be x hours.
As per the condition, Narayan will cover 60 km in x-4 hours.
Therefore, Speed of Partha = 60/x
And Speed of Narayan = 60/(x−4)
It is also given that Partha reaches the mid-point of A and B two hours before Narayan reaches B. Hence,
⇒ 30/60/x + 2 = 60/60/(x-4)
x/2+2 = x-4
x+4/2 = x-4
x+4 = 2x-8
x = 12
OR Partha will take 12 hours to cross 60 km.
=> Speed of Partha = 60/12=5 Kmph.