Physics statics calculations

Question

The question is : A metre rule of weight 1.0N is pivoted on a knife-edge at its centre of mass, supporting a weight of 5.0N and an unknown weight W. To balance the rule horizontally with the unknown weight on the 250mm mark of the rule, the position of the 5.0N weight needs to be at the 810mm mark

a Calculate the unknown weight.

b Calculate the support force on the rule from the knife-edge rule

I’ve worked out the unknown weight to be 6.2N but have no idea how to answer part b

Answer 1

b) answer is 12.2 N