  We derive upper and lower estimates of the area of unknown defects in the
form of either cavities or rigid inclusions in Mindlin-Reissner elastic plates
in terms of the difference $\delta W$ of the works exerted by boundary loads on
the defected and on the reference plate. It turns out that the upper estimates
depend linearly on $\delta W$, whereas the lower ones depend quadratically on
$\delta W$. These results continue a line of research concerning size estimates
of extreme inclusions in electric conductors, elastic bodies and plates.
