Simon recently received a credit card with an 25.25% nominal interest rate. With the card, he purchased an Apple iPhone 6 for $401.71. The minimum payment on the card is only $10 per month.

a) If Layla makes the minimum monthly payment and makes no other charges, how many months will it be before he pays off the card? Round to the nearest month.

b) If Layla makes monthly payments of $35, how many months will it be before he pays off the debt? Round to the nearest month.

Using formula if possible