Beginning inventory was 26000 i purchased 24000 and accepted 12000 in transfers i sold 39000 worth of food my ending inventory was 29000 what was my gross profit margin

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )