Redwood Corporation is considering two alternative investment proposals with the following​ data: Proposal X Proposal Y Investment ​$830,000 ​$510,000 Useful life 8 years 8 years Estimated annual net cash inflows for 8 years ​$135,000 ​$83,000 Residual value ​$50,000 ​$minus Depreciation method Straightminusline Straightminusline Required rate of return ​16% ​9% How long is the payback period for Proposal​ X?