Drill Problem 10-13 [LU 10-3 (1)] Given Principal $12,000, Interest Rate 10%, Time 240 days (use ordinary interest) Partial payments: On 100th day, $4,200 On 180th day, $2,600 a. Use the U.S. Rule to solve for total interest cost. (Use 360 days a year. Do not round intermediate calculations. Round your answer to the nearest cent.) Total interest cost $ b. Use the U.S. Rule to solve for balances. (Use 360 days a year. Do not round intermediate calculations. Round your answer to the nearest cent.) On 100th day On 180th day $ Balance after the payment c. Use the U.S. Rule to solve for final payment. (Use 360 days a year. Do not round intermediate calculations. Round your answer to the nearest cent.) Final payment $