After four years, mortgage rates drop to 8 percent for 30-year fixed-rate mortgages. You still have the old 10 percent mortgage you signed four years ago and you plan to live in the house for another five years. The total cost to refinance the mortgage is $3,000 including legal fees, closing costs and points. The rate o a five-year CD is 6 percent. Should you refinance your mortgage or invest the $3,000 in a CD? The 6 percent CD rate is your opportunity cost of capital.