Some friends on a hike leave at 9a.m. and return at 2p.m. They spend one-quarter of the total distance walking uphill, one-half walking on level ground, and one-quarter walking downhill. If their speed is 4 mph on level ground, 2 mph uphill, and 6 mph downhill, approximately how far did they walk? I came to the answer of 20 miles. Is this correct? Thanks