Which point on the graph tells you the amount one hat costs? A- (0,0) B-(1,5) C-(5,1) D-(2,10)

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! )