j. alexander airline company is considering expanding its territory. the company has the opportunity to purchase one of two different used airplanes. the first airplane (a) is expected to cost $1,200,000; it will enable the company to increase its annual cash inflow by $400,000 per year. the plane is expected to have a useful life of five years and no salvage value. the second plane (b) costs $2,300,000; it will enable the company to increase annual cash flow by $460,000 per year. this plane has an eight-year useful life and a zero salvage value. what is the payback period for each cash investment alternative?