The pie charts represent the distances covered by a boat moving upstream and downstream over seven days of a week. The total distance covered upstream...

The pie charts represent the distances covered by a boat moving upstream and downstream over seven days of a week. The total distance covered upstream is $1800 \text{ km}$ and downstream is $1500 \text{ km}$. The percentages of distances covered each day are as follows:

The table below shows the speed of the stream (in km/hr) on different days:

The speed of the boat in still water on Saturday was $21 \text{ km/hr}$. On Sunday, the speed of the boat in still water was $\frac{284}{7}$ less than that on Saturday. If the time taken by the boat to travel upstream on Saturday is $\frac{13}{16}$ times the time taken to travel downstream on Sunday, then find the time taken by the boat to cover a distance of $57.6 \text{ km}$ upstream when the speed of the stream is the same as that on Saturday.