Problem $2.$ A plastic block with shear modulus $G$ is bonded to a fixed base and to

a horizontal rigid plate to which a force $P$ is applied. Determine the maximum

thickness $t$ of the plastic block if the deflection of the plate is not to exceed a

small value $.$ The length and width of the block are $L$ and $b$ respectively. Assume

small deformation. $(4$ points$)$