Leah bought 3 boxes of birdseed. When she went to put them away, she discovered that she already had 5 boxes in the pantry. Her parrot eats 100 grams of seeds each week and her cockatiel eats 50 grams of seeds in a week. If each box of birdseed contains 225 grams, for how many weeks can she feed her birds without going back to the store?
Please reason step by step, and put your final answer within \boxed{}.
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