$1.)$ A thin rectangular$-$shape piezoceramic sensos $($use

properties of PSI$-5$ALE$),$ is under mechanical stress

$(2$MPa$),$ applied along the direction of polarization.

In addition, $4$ MPa stresses are applied to each of

two planes directions, i$.$e$.$ normal to the polarization

direction. $($a$)$ Obtain the electric field vector produced by

the applied stresses assuming that the electric

displacement is held equal to zero and $($b$)$ Obtain

only $E_3$ again with the new dielectric constant

obtained using electromechanical coupling factor kij.