Shawn Bixby borrowed $20,000 on a 210-day, 14% note. After 85 days, Shawn paid $2,300 on the note. On day 130, Shawn paid an additional $4,300. Use ordinary interest. a. Determine the total interest use the U.S. Rule. (Do not round intermediate calculations. Round your answer to the nearest cent.) Total interest b. Determine the ending balance due use the U.S. Rule. (Do not round intermediate calculations. Round your answer to the nearest cent.) Ending balance due