A student owes $400 in 3 months and $500 in twelve months. What single payment now will repay these debts if the interest rate is 12% compound quarterly for the first 6 months and 10% compound monthly afterwards?

On Monday at 1 p.m., when the ocean's surface was at an elevation of 2.2 feet, Winston went to a surf shop that was 8.2 feet above the ocean's surface. At 7 p.m. when the ocean's surface was at an elevation of -2.4 feet, Winston ate dinner at a restaurant whose deck was 10 feet above the ocean's surface.