What is the distance of the 450 N child from the fulcrum?

A 70N uniform plank 4m in length, rests with its center of mass on a fulcrum support. Two children weighing 600N and 450N, respectively sit on the opposite side of the fulcrum if the 600N child is 1.2m from the fulcrum at what distance from the fulcrum is the 450N child if the system is balanced.