Joe knows that adding a special grain supplement to his cows will produce more milk according to the following schedule:

1/3 2/6 3/8 4/10 5/11 6/12;

where the first number reports the total number of pounds of grain supplement, and the second number reports the total amount of milk produced. For example, 3/10 means that if the cow is fed 3 pounds of grain supplement, the cow will produce 10 units of milk.

How many pounds of grain supplement should Joe feed the cows if the farm receives $0.30 per unit of milk and the price of grain supplement is $0.50 per pound?