IRR

HI john, James Co plans to buy a machine costing $800,000, which will last for four years and then be sold for $50,000. The net cash flows are expected to be as follows: T1 T2 T3 T4 $244,000 $286,000 $374,000 $156,000 James has a target return on capital employed of 20%. The cost of capital is 10%. Using net present values calculated at 10% and at 20%, estimate the internal rate of return (IRR) to the nearest %. this question is form opentuition mock exam. i cant view how did he arrive the answer of IRR=15%.