(1 point) The commission charged for investing is $40 plus 1.4% of the principal. An investor purchases 500 shares at $15.95 a share, holds the stock for 28 weeks, and then sells the stock for $19.91 a share. (a) At the time the investor purchases, the investment's principal is dollars, the commission is for a total investment of dollars dollars. (b) At the time the investor sells, the principal is dollars, a commission of dollars is charged for a total return of dollars. (c) Based on the total investment you computed as the last answer in part (a), the total return you computed as the last answer in part (b), the time of 28 weeks (and there are 52 weeks in a year), using the Simple Interest Formula what annual rate of interest earned? r = so the annual interest rate (as a percent) is percent Your answer to the final question must be EXACT. If you have all questions but the last question go green, your answer is not exact. Replace the inexact work borrowed from parts (a) and (b) with exact values when answering the last question in part (c), or as a more useful general practice, use exact values for all questions in