To make homemade ice cream, you cool the milk and cream by immersing the container in ice and a concentrated solution of rock salt (NaCl) in water. If you want to have a water–salt solution that freezes at −10.°C, what mass of NaCl must you add to 3.0 kg of water? (Assume the van’t Hoff factor, i, for NaCl is 1.85.)