The plate shown in Fig. $7-32$a is fixed cannected along $AB$ and held in the horizontal guides at its top and bottom, $AD$ and $BC.$ If its right side $CD$ is given a uniform horizontal displacement of $2$ mm determine $($a$)$ the average normal strain along the diagonal $A{C}_1$ and $(b)$ the shear strain at $E$ relative to the $x,y$ axes