Julie bought a house with a $$100,000$ mortgage for $30$ years being

repaid with payments at the end of each month at an interest rate of $8\%$ compounded monthly. Compute the outstanding balance at the end of $10$ years immediately after the $120$th payment.

ANSWER: $$87724\mathrm{.}70$

If Julie pays an extra $$100$ each month in the preceding problem,

compute the outstanding balance at the end of $10$ years immediately after the $120$th payment.

ANSWER: $$69430\mathrm{.}10$

I just need the answer to the second question but step by step please.