The speed of boat in still water on Saturday was 21 km/hr. and that on Sunday was `28(4)/(7)%` less than tha on Saturday. Is the time taken by boat to travel upstream on Saturday is `1(3)/(16)` times than time taken to travel downstrean on Sunday, then find the time taken by the boat to cover a distance of `57.6` km upstream when the speed of stream is same as that of Saturday.

Options

A. 3 hrs
B. 2.5 hrs
C. 4 hrs
D. None of these