A solid conducting sphere of radius $r_{1}$ has a total charge of $+3 Q .$ It is placed inside (and concentric with) a conducting spherical shell of inner radius $r_{2}$ and outer radius $r_{3}$. Find the electric field in these regions: $r<r_{1}$, $r_{1}<r<r_{2}, r_{2}<r<r_{3}$, and $r>r_{3}$.