Exercise number 6. A company borrowed $66,000 to pay it back in seven equal annual installments. The amortization table of the promissory note is as follows:

a. What is the annual interest rate on this note?

b. Assume the annual payment is $12,000 (all other variables are the same, including the interest rate you calculated in part a), how much will the principal balance be due at the end of the seventh year?

\begin{tabular}{|c|r|r|r|r|} \hline & Pago & Inters & Principal & $66,000 \\ \hline 1 & 14,462 & 7,920 & 6,542 & 59,458 \\ \hline 2 & 14,462 & 7,135 & 7,327 & 52,131 \\ \hline 3 & 14,462 & 6,256 & 8,206 & 43,925 \\ \hline 4 & 14,462 & 5,271 & 9,191 & 34,735 \\ \hline 5 & 14,462 & 4,168 & 10,294 & 24,441 \\ \hline 6 & 14,462 & 2,933 & 11,529 & 12,912 \\ \hline 7 & 14,462 & 1,549 & 12,912 & (0) \\ \hline \end{tabular}