$5)$ A system consists of:

$-$ A conducting solid sphere of radius $30$ cm carries a net charge of $+200$ nC $,$ uniformly distributed throughout it$$ volume.

$-$ A conducting spherical shell with radius $50$ cm and a net charge of $-80$ nC $.$

$-$ A point charge of $\backslash ($ q$=-50\backslash$mathrm$\{$nC$\}\backslash )$ which placed at a distance $100$ cm from the center of the solid sphere.

a$.-$What is the magnitude of potential difference $\backslash ((\backslash$mathrm$\{$V$\})\backslash )$ at $20$ cm from the center of the solid sphere?

b$.$ What is the magnitude of the electric field $\backslash (($E$)\backslash )$ at $150$ cm from the center of the solid sphere?