uming complete dissociation of the solute, how many grams of must be added to 275mL ?

uming complete dissociation of the solute, how many grams of must be added to 275mL of water to produce a solution that freezes at -14.5 C? The freezing point for pure water is 0.0 and Kf is equal to 1.86 C/m.Express the m numerically in grams.