What is most important feature in capital recovery from the perspective of lenders and borrowers (less than 200 words)?

What is most important feature in sinking funds from the perspective of the one who is saving money (less than 200 words)?

Calculate the future equivalent at the end of 2017, at 8% per year of the following series of cash flows. You MUST use a linear gradient series with a constant amount (G) in your solution.

Years 2015 2013 2014 2016 2017 $400 $600 $800 $1,000 $1,200 F =