A rectangular gate that is $2$ m wide is located in the vertical wall of a tank containing

water as shown in the figure below. It is desired to have the gate open automatically

when the depth of water above the top of the gate reaches $18$ m $.($a$)$ At what distance, $d,$

should the frictionless horizontal shaft be located? $($b$)$ What is the magnitude of the force

on the gate when it is closed?

$($a$)d=$

$($b$)F_R=$