Bookies Inc. sells paperbacks to airport stores. The books cost $1 in material and $1.50 in conversion costs. Selling commission to salespeople average .$50 per book. Fixed overhead costs are $10,000 per month for facility rental, $2,000 per month for accounting, and $3,000 per month for base salary of salespeople. Selling prices average $7.50 per month. How many books must be sold each month to make a profit of $10,000?