A firm is evaluating the purchase of a new machine that costs $200,000 and has a useful life of 5 years with no salvage value. The machine is expected to save $60,000 annually in operating costs. The firm's tax rate is 25%, and its required rate of return is 8%. Calculate the NPV and IRR for the machine.

Requirements:

1. Calculate the NPV of the machine.
2. Determine the IRR.
3. Assess whether the machine should be purchased.
4. Discuss the impact of tax rate changes on NPV and IRR.
5. Comment on the sensitivity of the project to changes in the required rate of return.