Can you explain how to solve this math problem: Bill milked his cow and got 16 gallons of milk. He turned 1/4 into sour cream, 1/4 into butter, and kept the rest as whole milk. It takes 4 gallons of milk to make one gallon of butter and 2 gallons of milk to make 1 gallon of sour cream. If Bill sells butter for $5/gallon, sour cream for $6/gallon, and whole milk for $3/gallon, how much money does he make?