Carlos famous punch calls for 2 L of mango juice only mango juice she can find is sold in 500 mL cartons how many cartons of mango juice does Carly need to buy

If 30 lb of rice and 30 lb of potatoes cost ? $27.60? , and 20 lb of rice and 12 lb of potatoes cost ? $15.04? , how much will 10 lb of rice and 50 lb of potatoes? cost?