A $500 balance on a card with 15.99% (0.1599) APR:
[tex]\begin{gathered} Monthly\text{f}\imaginaryI nance=500*\frac{0.1599}{12} \\ \\ Monthly\text{f}\imaginaryI nance=6.66 \end{gathered}[/tex]A $400 card with a 25.99% (0.2599)APR:
[tex]\begin{gathered} Monthly\text{f}\mathrm{i}nance=400*\frac{0.2599}{12} \\ \\ Monthly\text{f}\mathrm{i}nance=8.66 \end{gathered}[/tex]