50 POINTS
A pencil at a stationery store costs $1, and a pen costs $1.50. Shawn spent $12 at the store. He bought a total of 9 items. Which system of equations can be used to find the number of pencils (x) and pens (y) he bought?

a
1.5x + y = 12
x = 9y

b
x + 1.5y = 12
x + y = 9

c
x + 9y = 12
x = 1.5y

d
9x + y = 12
x = 1.5y