A Solution Is Made by Dissolving 0

A solution is made by dissolving 0.840 moles of sodium hydroxide in 300.0 g of water. If the van't Hoff factor, i, for this particular concentration is 1.70, what is the expected freezing point of this solution? K_f = 1.86 °C m^-1.

A) +0.80°C
B) -2.66°C
C) +3.06°C
D) -8.85°C
E) -9.97°C