How would the formula for calculating time in days (given principal, interest, and rate) change if exact interest is used in contrast to ordinary interest?

When a borrower is often confronted as a stated interest and an effective interest rate what is the difference and which one should the financial manager recognize as the true cost of borrowing? The effective interest rate is always calculated as if compounded annually. The effective rate is...

I have student loans in the amount of $20000. Through consolidation and never missing a payment I have the interest loan at 2.50% (simple interest). Montly payment is approx $100. I am getting an APY no a Savings account at 4.75%. I have savings around $5K and growing. I need cash for other...