I am working on an example problem. I noticed that the cash flows are different every year. So I set up a schedule to calculate unrecovered investments. I came up with 6.5 years as a payback period, but this was marked incorrectly. So I am wondering what I did wrong.

Attached is the Excel workbook with my calculations. If you can give me a detailed explanation, that would be appreciated.

Given: The management team of Aramak, a company, would like to invest in a multipurpose with the following cash flows: Year Investment 1 2 3 4 5 6 7 8 9 10 Cash Flow 75,000 7,000 My response 6,000 12,000 18,000 17,000 20,000 18,000 16,000 14,000 10,000 13,000 1. Determine the payback period of the investment. Payback period (Round your response to 1 decimal place) Years My work The management team of Aramak, a company, would like to invest in a multipurpose with the following cash flows: Year Investment 1 2 3 4 5 6 7 8 9 10 Cash Flow 75,000 7,000 Unrecovered Investment -69,000 Investment is the outflow and cashflow is the inflow. -64,000 -46,000 -29,000 -9,000 6,000 12,000 18,000 17,000 20,000 18,000 16,000 14,000 10,000 13,000 1. Determine the payback period of the investment. Payback period (Round your response to 1 decimal place) 6.5 Years 6.5 years was marked wrong. Why? because 9,000/18,000 = 0.5 + 6 yrs = 6.5