A uniform plank is 6.0 m long and weighs 80 N.It is balanced

A uniform plank is 6.0 m long and weighs 80 N.It is balanced on asawhorse at its center.An additional 160 N weight is now placed on the leftend of the plank.To keep the plank balanced,it must be moved what distance tothe right?
A) 6.0m
B) 2.0 m
C) 1.5m
D) 1.0m
E) 0.50m
为啥