A company is analyzing the purchase of new equipment with the following details:

• Equipment cost: ¥500 million
• Estimated life: 8 years
• Annual savings: ¥80 million
• Depreciation: Sum of the years' digits method
• Salvage value: ¥20 million
• Discount rate: 6%

Required:

1. Calculate the annual depreciation expenses.
2. Determine the NPV of the equipment purchase.
3. Compute the IRR.
4. Calculate the payback period.
5. Advise on the purchase decision based on financial metrics.