Given that Martin's unpaid credit card balance was $1539.39 and his APR is 13.2%.
APR is the annual interest rate, to get the monthly interest rate, we divide the APR by 12.
Thus, monthly interest rate is [tex]i= \frac{13.2\%}{12} =1.1%[/tex]
The interest charge for the month is given by [tex]I=Pi[/tex], where P is the previous balance, i is the monthly interest rate.
Thus, interest charge is [tex]I=1,539.39(0.011)=1,539.39(0.011)=\$16.93 [/tex]
The balance after the monthly interest charge = $1,539.39 + $16.93 = $1,556.32
Therefore, the balance after the new transaction is given by $1,556.32 + $178 = $1734.32
