It would have taken you 5:30 for each mile. 55/10 is 5.5 thats 5 and a half, half a minute is 30 seconds. so 5 minutes and 30 seconds
12 1/4 feet wide stream so it is 1 feet and 9 inches shorter
The percent to 300 out of 12 is 144
Let , side lawn is a.
Area of boundary is :

Now, total cost is given by :

Area left is :

Price to empty space with turfs is :

Therefore, the cost of covering the empty space with turfs at the rate of Rs 20 per sq. metre is Rs 262500.
Hence, this is the required solution.