Each small kite costs $4, while each large kite costs $7. If the total money collected selling kites is $150, and 30 kites are sold, which system of equations can be used to find out how many of each size kite are sold?

Let s be the small kites and l be the number of large kites.


a. 4l+7s=150
s+l=30
b. 7l+4s=150
s+l+30
c. 7l+4s+30
s+l=150
d. l+4s=150
s+7l=30