Charles is going to purchase a new car that has a list price of $21,450. he is planning on trading in his good-condition 2004 dodge neon and financing the rest of the cost over three years, paying monthly. his finance plan has an interest rate of 12.28%, compounded monthly. charles will also be responsible for 6.88% sales tax, a $1,089 vehicle registration fee, and a $124 documentation fee. if the dealer gives charles 80% of the listed trade-in price on his car, once the financing is paid off, what percent of the total amount paid will the interest be? (consider the trade-in to be a reduction in the amount paid.) dodge cars in good condition model/year 2004 2005 2006 2007 2008 viper $7,068 $7,225 $7,626 $7,901 $8,116 neon $6,591 $6,777 $6,822 $7,191 $7,440 intrepid $8,285 $8,579 $8,699 $9,030 $9,121 dakota $7,578 $7,763 $7,945 $8,313 $8,581 a. 17.64% b. 15.67% c. 16.70% d. 12.86%