Annual credit sales of Nadak Co. total $680 million. The firm gives a 2% cash discount for payment within 10 days of the invoice date; 90% of Nadak's accounts receivable are paid within the discount period. Required: a. What is the total amount of cash discounts allowed in a year? (Enter your answer in millions rounded to 2 decimal places.) Total amount million b. Calculate the approximate annual rate of return on investment that Nadak Co.'s cash discount terms represent to customers who take the discount. (Assume a credit period of 30 days and 360-days year). (Round intermediate calculations to nearest whole percentage.) ROI %