a. On a hiking trip Bob and his two friends hiked 15 miles the first day, 10 miles on the second and 7 miles on the third day. If they walked a total of 60 miles over a 5 day trip and did not walk more than 18 miles on any one day, how many miles could they have walked each of the last two days? b. If they hiked at a top speed of 6 miles per hour on flat terrain, but had to slow down when climbing hills could they have have made the trip in a single 10 hour day of sunshine? Support your answer.