Nowadays it is very important to reduce​ one's carbon​ "footprint" (how much carbon we produce in our daily​ lifestyles). Minimizing the use of fossil fuels and instead resorting to renewable sources of energy​ (e. g., solar​ energy) are vital to a​ "sustainable" lifestyle and a lower carbon footprint.​ Let's consider solar panels that prewarm the water fed to a conventional home water heater. The solar panels have an installed cost of ​$​, and they reduce the​ homeowner's energy bill by ​$ per month. The residual value of the solar panels is negligible at the end of their ​-year life. What is the annual effective IRR of this​ investment? The annual effective IRR of this investment is nothing​%. ​(Round to two decimal​ places.)