Kailey and Macy paddle a canoe at a rate of 6 miles per hour in still water. They travel downstream for 10 miles, and to their distress, they have to paddle back upstream 10 miles because no one was was there to pick them up at the end of their canoe trip. The total trip took 7 hours. Assuming they paddled at the same rate downstream and upstream, how fast was the speed of the water's current in miles per hour? Round your answer to 3 decimal places.