An income statement for Sam's Bookstore for the first quarter of the year is presented below: Sam's Bookstore Income Statement For Quarter Ended March 31 Sales $ 900,000 Cost of goods sold 630,000 Gross margin 270,000 Selling and administrative expenses Selling $ 100,000 Administrative 104,000 204,000 Net operating income $ 66,000 On average, a book sells for $50. Variable selling expenses are $5 per book with the remaining selling expenses b The variable administrative expenses are 4% of sales with the remainder being fixed. The cost formula for selling and administrative expenses with "X" equal to the number of books sold is: