a
$\frac{{{R_1}}}{{{R_2}}} = \frac{{(1 + \alpha {t_1})}}{{(1 + \alpha {t_2})}}$
$\frac{{10}}{{{R_2}}} = \frac{{(1 + 5 \times {{10}^{ - 3}} \times 20)}}{{(1 + 5 \times {{10}^{ - 3}} \times 120)}}$
${R_2} \approx 15\,\Omega $
Also $\frac{{{i_1}}}{{{i_2}}} = \frac{{{R_2}}}{{{R_1}}}$
$\frac{{30}}{{{i_2}}} = \frac{{15}}{{10}}$
${i_2} = 20\,mA$