Abigail spent $100 on a new edition of the personal finance textbook rather than $75 for a used copy. the additional cost for the new copy is called the

Abigail spent $100 on a new edition of the personal finance textbook rather than $75 for a used copy. Thee additional cost for the new copy is called the marginal cost. Marginal cost denotes the change in total cost for making one additional unit of an item. In this case the personal finance textbook is the additional unit.

month 1 start amount =$3287.90 interest=(3287.90x0.0145/12)3.97 total to pay=$3291.81 paid =$1200 balance =$2,091.87

month 2 starting amount= $2,091.87 interest =$25.28 total to pay =$2117.15 paid =$1200 balance $917.15

month 3 starting amount =$917.15 interest =$11.08 total to pay =$928.23 paid =$928.23 balance =$0 total to pay 1200+1200+928.23 = $3328.23 it will take 3 months to pay a total of $3328.23

answer; i believe the correct answer is (75 years);