Answer
Please see the work below.
Work Step by Step
We know that
$\Delta T_f=K_fc_m$
We plug in the known value to obtain:
$\Delta T_f=1.858\frac{C^{\circ}}{m}\times (11.57m)=21.4C^{\circ}$
Hence $T_f=0.0C^{\circ}-21.4C^{\circ}=-21.4C^{\circ}$