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