Two spherical shells have a common center. A $-1\mathrm{.}50\backslash$times $10-6$ C charge is spread uniformly over the inner shell, which has a radius of $0\mathrm{.}050$ m$.$ A $+5\mathrm{.}00\backslash$times $10-6$ C charge is spread uniformly over the outer shell, which has a radius of $0\mathrm{.}15$ m$.$ Find the magnitude and direction of the electric field at a distance $($measured from the common center$)$ of

$($a$)0\mathrm{.}20$ m$,$

E $=$

$($b$)0\mathrm{.}10$ m$,$

E $=$

$($c$)0\mathrm{.}025$ m$.$

E $=$