Two Children Seat Themselves on a Seesaw

Multiple Choice

Two children seat themselves on a seesaw.The one on the left has a weight of 400 N while the one on the right weighs 300 N.The fulcrum is at the midpoint of the seesaw.If the child on the right is not at the end but is 1.50 m from the fulcrum and the seesaw is balanced,what is the torque provided by the weight of the child on the left? (Take ccw as positive. )

A) 600 N·m
B) 450 N·m
C) -600 N·m
D) -450 N·m