Based on before information. How should I answer no.6 and no.8

3. A tractor and mower costs $28,000. At the present time. You can earn a net return of $6,700 at the ends of years 1 through 6. The equipment will be worth $4,000 when you are done using it at the end of year 6. Calculate the net present value of the tractor- mower investment using a discount rate of 8%. 4. A saw mill for cutting wood costs $24,000 at the present time. You can earn a net return of $6,800 at the end of year 1, $7,000 at the end of year 2, $7,200 at the end of year 3, and $7,300 at the end of year 4. The equipment will be worth $7,500 when you are done using it at the end of year 4. Calculate the net present value of the mill using a discount rate of 8%. 5. Based on NPV, which investment looks better? Explain why this comparison is not a good idea