Rates on 30-year mortgages fell to 6.06% this week from 6.16% last week. A year ago, the rate averaged 7.04%. Rates on 15-year fixed-rate mortgages dropping to 5.38%. MCLEAN, Va. — The average long-term U.S. mortgage rate is now down to its lowest level in more than three years. The benchmark 30-year fixed rate mortgage rate eased to 6.06% this week, down from 6.16% last week, mortgage buyer...