What is a. b. and c? Please help. Thank you.

Your firm spends $501,000 per year in regular maintenance of its equipment. Due to the economic downturn, the firm considers forgoing these maintenance expenses for the next 3 years. If it does so, it expects it will need to spend $1.8 million in year 4 replacing failed equipment. a. What is the IRR of the decision to forgo maintenance of the equipment? b. Does the IRR rule work for this decision? c. For what costs of capital (COC) is forgoing maintenance a good decision