I have a final coming up and she said we have a question exactly like this but with different numbers. Could you help me as detailed as possible? we need to show all our work when we take the final in order to get credit. Thank you so much in advance!

Billy McMahon is interested in buying a waterfront vacation condo and has saved $100,000 for the down payment. His plans call for making additional monthly deposits into an investment account over the next 12 months. Billy McMahon wants to make the purchase 18 months from today and wants to have $240,000 saved up for the down payment.

1. What is the amount of each of the additional payments he must make for his plan to work out? Assume Billy can earn 2% annual return in his investment account.
2. If Billy takes out a 30-year, $960,000 mortgage at 4%, what will his mortgage payments be?