Mrs. gibbs goes to the store to buy aa and 9v batteries. she needs at least 6 aa batteries. in all, she wants to buy at least 20 batteries. the store has 12 aa batteries and 15 9v batteries in stock. the graph shows the feasible region, where x represents the number of aa batteries and y represents the number of 9v batteries. which ordered pairs meet all the constraints and make sense in the context of the situation? select each correct answer.