Heat produced in a wire of resistance R in time t is
$H=I^{2}Rt$
Heat required to raise the temperature of a wire by $\Delta\,T$ is
$\therefore Q=ms \Delta\, T$
$Q=H$
$ms \Delta\,T=I^{2}Rt$ or $\Delta T \propto I^{2}$
$\therefore \frac{\Delta T_{2}}{\Delta T_{1}}=\left(\frac{I_{2}}{I_{1}}\right)^{2}$
$\left(\frac{3I_{1}}{I_{1}}\right)=9$
$\Delta T_{2}=\Delta T_{1}\times9=4^{\circ}C\times9$
$=36^{\circ}C$