A company is contemplating to purchase a machine. Machines A is available costing Rs$.500000.$ In comparing the profitability of the machines $,$ a discounted rate of $10\%$ is to be used $.$ Earnings after taxation are expected as follows :

Year Machine A $($Rs$)$

I $150000$

II $200000$

III $250000$

IV $150000$

V $100000$

Compute Pay Back period and ARR assuming Straight Line Method of Depreciation.