Problem 21-2 Optimal Cash Balance (L03) Assume that Everyman's Bookstore uses up cash at a steady rate of $250,000 per year. The interest rate is 3% and each sale of securities costs $120. a. How many times a year should the store sell securities? (Round your answer to 2 decimal places.) Times per year times b. What is its average cash balance? (Round your answer to the nearest whole dollar.) Average cash balance