I need in depth calculation

5-55. The upturned wingtips on jet aircraft reduce drag and increase lift. Wingtips save on fuel consumption, averaging 4% of the total fuel bill. A single set of wingtips can annually save 45,000 gallons of jet fuel costing $3 per gallon. (Fuel is the biggest operating expense of an airline company.) Furthermore, 100 metric tons of carbon dioxide emissions each year will be avoided, and maintenance expenses will be reduced. Wingtips cost $1 million to install. The airline company's MARR is 20%. Considering only the fuel savings, what is the simple payback period for the wingtips? What is the discounted payback period? (5.8)