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How much would the freezing point of water decrease if 4 mol of NaCl were added to 1 kg of water (Kf = 1.86°C/(mol/kg) for water and i = 2 for NaCl)?

A. 14.88°C 
B. 3.72°C
C. 7.44°C
D. 1.86°C

PLEASE ANSWER ASAP