A walk around the basement reveals there are many areas of uninsulated pipes, as follows: steam heating pipes- 100' of 3" pipe; domestic hot water (DHW)- 60' of 1 1/2" pipe. You calcualte that insulating the pipes would save 500 gallons (in a normal weather year). Given an energy cost of $1.5 per gallon and an installed cost of $10 per linear foot for insulation of the 3" pipe and $6 per linear foot for insulation of the 1.5" pipe, what would be the sample payback in years for insulating the DHW pipes?