there's no 50-mile hike requirement -- all the hikes are to be done in a single day and 20 is the maximum length for good reason
the sum total of all the required hikes is 70 miles: 5, 10, 10, 10, 15, 20
the sum total of all the required hikes is 70 miles: 5, 10, 10, 10, 15, 20