Answer:
6.75 years
No
Explanation:
The payback period calculates how long it takes to recover the amount invested in a project.
Explanations on how the payback period is calculated can be found in the attached image.
If the cash flow of the last year was increased , it won't affect the payback period because the amount invested has already been recovered between the 6th and 7th year. Therefore, the last cash flow won't be used in calculating the payback period.
I hope my answer helps you