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 $840,000 Cost of goods sold 520,000 Gross margin 320,000 Selling and administrative expenses Selling $111,000 Administration 126,000 237,000 Net operating income $ 83,000 On average, a book sells for $70. Variable selling expenses are $5 per book with the remaining selling expenses being fixed. 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: Multiple Choice Y = $143,400 + $7.80X Y = $116,600 + $5.00X Y = $143,400+ $10.60X Y-$116,600 + $7.80X