Consider a unit cube occupying the region: 0 x 1, 0 y 1, 0 Z 1. The following displacement field is applied to the cube (with a > 0 but small): u = ay v = -ax W = 0 a) Sketch the undeformed and deformed shapes of the cube in the x-y plane. [10 points] b) Show that the above displacement field describes rigid body motion. [10 points]