Question 252251
I think I am on the right track here . . . 

Part 1:pay off within 90 days means purchase price plus sales tax.  699 * (1.0825) = $756.67

Part 2: Buys december 15. 90 days in non leap year = March 15; 90 days in leap year = March 16. The finance company I think will use ordinary interest.

part 3: If she pays on April 1st, that is 16 days late. She pays 699 + 8.25% sales tax + .268(90/365) + .02*699*1 = $770.71

part 4: Compared to payoff within 90 days, it cost her $14.04. This is 14.04/699 = 2%.