Tina is trying to determine the prices in dollars she should charge for lemonade (PL) and orange juice (PO) at her lemonade stand. She believes she can sell 50 10(PL) - 20(PO) glasses of orange juice per day and 100 - 30(PL) 10(PO) glasses of lemonade per day. If Tina wants to sell 20 glasses of orange juice per day and 90 glasses of lemonade per day, what prices should she charge