b
\(\frac{{{i_1}}}{{{i_2}}}\,\,\, = \,\,\,\frac{{{R_2}}}{{{R_1}}}\,\,\, = \,\,\frac{{\rho \,{\ell _2}}}{{{A_2}}}\,\, \times \,\,\frac{{{A_1}}}{{\rho \,{\ell _1}}}\)

\( = \,\,\frac{{{\ell _2}}}{{{\ell _1}}}\,\, \times \,\,\,\frac{{r_1^2}}{{r_2^2}}\,\, = \,\,\frac{3}{4}\,\, \times \,\,{\left( {\frac{2}{3}} \right)^2}\)  \( = \,\,\frac{1}{3}\)