A rancher has to mix three types of feed for her cattle. The following analysis shows the amounts per bag of grain:
Grain Protein (kg) Carbohydrates (kg) Sodium (kg)
A 7 88 1
B 6 90 1
C 10 70 2
How many bags of each type of grain should she mix to provide 71kg of protein, 854 kg of carbohydrates and 12kg of sodium?