Linear Proramming: Problem with three products and three additives plus a base

Incredible indelible ink company mixes three additives, A1,A2, A3 to a base in different proportions to obtain different colors of ink.
Red ink is obtained by mixing A1, A2, and A3 in the ration of 3:1:2, blue ink in the ratio of 2:3:4, and green in the ratio of 1:2:3.
After these additives are mixed, an equal amount of base is added for each color. The company currently has 1000 gallons of A1, 1500 of A2, 2000 of A3, and 4000 of base. Given that the selling price per gallon for each type on ink is the same, formulate a LP model to determine how these resources should be used to obtain the maximum revenue.