Liquid A has 10 grams of element X per liter. Liquid B has 15 milligrams of element Y per (there are 1000 milligrams in a gram and 1000 in a liter). It is desired to make 140 grams of molecule Z. To make 18 grams of Z requires 2 grams of X and 16 grams of Y. How many liters of each liquid should be used?