James and Karen have just moved into a new home their homeowner's insurance policy is $590 each year their insurance company is offering a 9% discount if they installed dealt bolt logs on all exterior doors the couple could also receive a 5% discount if they install smoke detectors on each floor they have contacted a local locksmith who will provide and install dead bolt locks on the 2 exterior doors for $70 each. At the hardware stores smock detectors cost $30 each in the home has 2 floors. James and Karen plan to install the smoke detectors themselves, assuming they're insurance rates remain the same how many years will it take them to earn back in this counts the cost of the smoke detectors. round you answer to in years to the nearest whole number.