Hi, I have been having trouble with this question. Can you prove a step by step explanation? Thanks.

Because of pressure to "complete" a road project, the bike path that goes with it is being postponed. Doing the bike path now would cost $35,800. Instead, this feature will be included in the transportation improvement program package that is now being assembled. Because of the state and federal budget cycles, the bike path will be built 3 years from now. The expected cost of doing it then is $68,000. What is the implied interest rate for postponing the bike path?