(a) (i) Calculate the freezing point of a solution when $10\cdot5 \text{ g}$ of $\text{MgBr}_2$ was dissolved in $250 \text{ g}$ of water, assuming $\text{MgBr}_2$ undergoes complete dissociation. (Given : Molar mass of $\text{MgBr}_2 = 184 \text{ g mol}^{-1}$, $\text{K}_\text{f} \text{ for water} = 1\cdot86 \text{ K kg mol}^{-1}$)