A student carried out an experiment to separate pure sodium chloride from a rock salt mixture.
The student started with 7.8 g7.8\text{ g}7.8 g of the rock salt mixture and successfully recovered 2.7 g2.7\text{ g}2.7 g of pure sodium chloride.
Calculate the mass of pure sodium chloride that could be recovered from 12.5 g12.5\text{ g}12.5 g of the same rock salt mixture, assuming the mixture is uniform.
Give your answer to 3 significant figures.