Casein, a dairy product used in making cheese, contains 25% moisture when wet. A dairy sells this product for $40/100 kg. If requested, they will dry the casein to 12% moisture. The drying costs are $5/100 kg of water removed. Assume that that the dairy has 1000 kg of the original product (wet casein) that will be dried to 12% moisture and then sold. How much dried casein is produced (in kg)?

The answer is 852 (with margin 1). Why is it?