how can it be done using cash flow digrams and formulas

1. Company X purchased a new machine for 25000 $ by life span of 10 years, expecting to earn 7500 $ as a yearly income from year 4 thereafter. It is assumed that its salvage value will be 31000$. Unexpectedly, from year 7, annual income starting to decrease by 300$ , Moreover at the end of 9th year due to a big collapse in the company the machine will be going to get rid of the production line totally(useless). Determine the real rate of return (ROR)