Please help solve part b

In this problem, we consider replacing an existing electrical water heater with an array of solar panels. The net installed investment cost of the panels is $1,440 ( $1,800 less a 20% tax credif from the government). Based on an energy audit, the existing water heater uses 180 kilowatt hours (kWh) of electricity per month, so at $0.11 per KWh, the cost of operating the water heater is $19.8 per month Assuming the solar panels can sive the entire cost of heating water with electricity, answer the following questions. a. What is the simple payback period for the solar panels? b. What is the IRR of this imvestment if the solar panels have a Me of 8 years? a. The simple payback period is months. (Round to the nearest whole number) b. The IRR of the investment is per month. (Round to two docimal places.)