The supermarket sells juice in 16- and 32-ounce bottles. If Warren wants to bring home 144 ounces of juice in 7 separate bottles, which system of equations should he solve to determine how many 16- and 32-ounce bottles to buy? (Let x represent the number of 16-ounce bottles and y represent the number of 32-ounce bottles.)
A. 32x+16y=144 x+y=7
B. 16x+32y=144 x+y=7
C. 32x+16y=144 x+y=144
D. 16x+32y=7 x+y=32