A company is considering whether to purchase some machinery that will cost £100 000 but that is expected to give rise to additional cash inflows of £50 000 per annum for four years. The cost of capital is 10% and taxation is at the rate of 35%. The machinery is eligible for 25% annual writing down allowances . It 1s anticipated that the machinery will be sold at the end of year 4 at its written down value for taxation purposes. Calculate the net present value.