Mortgage rates dropped slightly last week, with fixed-rate loans decreasing 0.06 percentage point and adjustable-rate deals falling 0.01 percentage point, the Federal Home Loan Mortgage Corp. said. The agency, which buys mortgages from lenders and packages them as securities for sale to investors, said fixed-rate loans reached 10.60% last week, down from 10.66% the week before. Adjustable-rate mortgages averaged 7.97%, down from 7.98% a week earlier. The fixed-rate average is for a 30-year loan covering 80% of a home's cost. The average adjustable-rate mortgage also is for 30 years but for 75% of the home price.