please help me solve this, my final answer was 450 but that was incorrect

You have credit card debt of $30,000 that has an APR (monthly compounding) of 18%. Each month you pay the minimum monthly payment. You are required to pay only the outstanding interest. You have received an offer in the mail for an otherwise identical credit card with an APR of 12%. After considering all your alternatives, you decide to switch cards, roll over the outstanding balance on the old card into the new card, and borrow additional money as well. How much can you borrow today on the new card without changing the minimum monthly payment you will be required to pay? (Note: Be careful not to round any intermediate steps less than six decimal places.) You can borrow $ on the new card without changing the minimum monthly payment you will be required to pay. (Round to the nearest dollar.)