4 A manufacturer buys a machine for Rs. 50,000 and its expected life is 10 years. The annual running costs for machine are Rs. 8,000 for first five years after which the costs increase per year by Rs. 2,000. If the money is worth 10% per year, when the machine should be replaced? Assume that the scrap value of the machine is nil. (PWF @10% for 1-10 years are 0.9091, 0.8264, 0.7513, 0.6830, 0.6209, 0.5645, 0.5132, 0.4665, 0.4241 and 0.3855 respectively). (CRF@ 10% for 1-10 years 1.10, 0.5762, 0.4021, 0.3155, 0.2638, 0.2296, 0.2054, 0.1874, 0.1736 and 0.1628)