c
\(\oint \overrightarrow{ E } \cdot d \overrightarrow{ s }=\frac{ Q _{\text {in }}}{\varepsilon_{ o }}\)

\(E .4 \pi r ^{2}=\frac{\int_{0}^{ r } \rho_{ o }\left(\frac{3}{4}-\frac{ r }{ R }\right) 4 \pi r ^{2} dr }{\varepsilon_{0}}\)

\(E 4 \pi r ^{2}=\frac{\rho_{ o } 4 \pi}{\varepsilon_{ o }}\left(\frac{3}{4} \frac{ r ^{3}}{3}-\frac{ r ^{4}}{4 R }\right)\)

\(Er { }^{2}=\frac{\rho_{ o } r ^{3}}{4 \varepsilon_{ o }}\left\{1-\frac{ r }{ R }\right\}\)

\(E =\frac{\rho_{0} r }{4 \varepsilon_{ o }}\left\{1-\frac{ r }{ R }\right\}\)