PLEASE HELP! 20 POINTS
The speed of the current in a river is 6mph. A ferry operator who works that part of the river is looking to buy a new boat. Every day his route takes him 22.5 miles each way against the current and back to his dock and he needs to make this trip in a total of 9 hours. He had a boat in mind but he can only test it on a lake where there is no current. How fast must the boat go on the lake in order to serve his needs? PLEASE SHOW ALL WORK