A fund-raising committee is selling two types of coupon books: standard and deluxe. Each standard book brings in $12 in revenue, and each deluxe book brings in $18 in revenue. The committee must raise at least $1,260 to cover its costs but can print no more than 100 books in total. If x is the number of standard books printed and y is the number of deluxe books printed, which system of inequalities correctly represents these constraints?