Some Partial Answers

2f)
The interest compounds on the remaining balance, and the balance decreases as we pay the loan off, so the interest is largest during the first month and decreases thereafter. Thus the average interest would be much lower

2i)
112420 - 82464.39 = 29955.61 saved

3e)
The 5% lent rate marks the expected returns if all the money is lent out and paid back. It stayed constant. The average earned rate fluctuates and captures the rate the fund actually receives in a given timeframe-- the cities couldn't find enough borrowers and some that borrowed didn't pay what they owed, so the average earned rate was lower.