Gilda would do anything for Luna, her 11- year-old cat. Until recently, she had been paying an animal hospital $22.50 every tow weeks for a 10 pound bag of vitamin enriced organic cat food designed for older cats. On Wednesday, Gilda called a local pet store. The store stock food similar to the one she buys at the animal hospital, but it is not organic. The store sells 25 pound bags for $59.55 and 50-pound bags for $99.50. Calculate the best buy among the three different sized bags of cat food. Would the lowest priced cat food be the best choice? Why or why not?