Austin Mini-Fridge Store's income statement for the current month is as follows: Sales revenue Cost of goods sold Gross profit Selling and administrative expenses Selling expenses Administrative expenses Operating income (50,000) (52,000) $450,000 (315,000) $135,000 (102,000) $33,000 Each mini-fridge sells for $150. Variable selling expenses are $9 per mini-fridge, and the remainder of the selling expenses are fixed. Variable administrative expenses are 7% of sales revenue, and the remainder of the administrative expenses are fixed. Assume "Y" equals the total selling and administrative expenses a "X" equals the total number of mini-fridges sold. What is the mixed cost formula for total selling and administrative expenses?