The cost of a new machine is $110,000 and it is expected to reduce the labour cost by $30,000 per year. The salvage value of the machine at the end of year six is expected to be $20,000. If the after-tax MARR of the company is 9% and the tax rate is 55% and the depreciation rate is 20%:

a) Determine the exact after-tax IRR for this investment?

b) Determine the approximate after-tax IRR?

c) Should the company buy this machine? Please show the calculation or the method you use to solve this question

Don't just show up an excel table with the answers, I really want to how to solve this kind of question