a. If the interest rate is 1% per month, what will be the change in the firm's total monthly profits on a present value basis if credit is offered to all customers? (Do not round intermediate calculations. Round your answer to 2 decimal places.) Change in total monthly profit $ 2,051.40 b. If the interest rate is 1.5% per month, what will be the change in the firm's total monthly profits on a present value basis if credit is offered to all customers? (Do not round intermediate calculations. Round your answer to 2 decimal places. Negative amount should be indicated by a minus sign.) Change in total monthly profit c. Assume the interest rate is 1.5% per month but the firm can offer the credit only as a special deal to new customers, while existing customers will continue to pay cash on delivery. What will be the change in the firm's total monthly profits on a present value basis under these conditions? (Do not round intermediate calculations. Round your answer to 2 decimal places.) Change in total monthly profit