For every convex compact set $K$ of area $1$ in $\mathbb{R}^2$, among all ellipses of area $1$ there exists an ellipse $E$ such that the area of the symmetric difference between $K$ and $E$ is smallest possible.
Questions.
(a) Is $E$ unique?
(b) If the answer is "yes", does the same hold for the analogous question in higher dimensions?