Wow! Classic case of SO MUCH spreadsheet that one cannot possibly have any understanding of what is going on. I do hope your grade isn't based on understanding this bloated spreadsheet.

Time Map:

Loan: PV = 90000

Payoff PV w/o Lump = 90000 = 3645(v^1 + v^2 + v^3 + ... + v^n) -- We'll need "n", the total number of regular quarterly payments?

Payoff PV w/4yr Lump = 90000 = 10000v^16 + 3645(v^1 + v^2 + v^3 + ... + v^m) -- We'll need "m", the total number of regular quarterly payments?

Payoff PV w/2yr Lump = 90000 = 10000v^8 + 3645(v^1 + v^2 + v^3 + ... + v^q) -- We'll need "q", the total number of regular quarterly payments?

Note: m and q should be 3-ish less than n. Why?

Note: n, m, and q could be non-integer.

1) I'm going to assume you know how to add up a geometric series. Please demonstrate.

2) I'm going to make you tell me the right value for "v". It has something to do with Quarterly, but not everything, since compounding is Semi-Annual.

3) That's the information we need, but we still can't answer the "how much interest" questions. It's not far from where we are.