Answer:
b. $133.92
Explanation:
Around $133.92 percent, in this case Marcia has to start paying off higher rates on her credit cards, because with those monthly payments she will never be able to pay off those debts, cause the interests rates are higher than the actual monthly payment she is putting. But by changing fmor the 16% APR to the 12% APR she can save around $133.92 dollars after 4 years.