Hello I'm completely confused on how to solve this sample problem (a b and c) ? Can a, b , c be solved so I can use this as a example

9-75 A newspaper is considering buying lock vend in ing machines to replace open newspaper racks the downtown area. The vending machines cost $45 each. It is expected that the annual revenue from sel ing the same quantity of newspapers will increase $12 per vending machine. The useful life of the vending machine is unknown. (a) To determine the sensitivity of rate of retum to useful life, prepare a graph for rate of versus useful life for lives up to 8 years. retun (b) If the newspaper requires a 12% rate te of retun in what minimum useful life must it obt the vending machines? e rate of return if the vendig last indefinitely? (c) What would be the rate of retu rn if th machines were to last indefinit Rental