Sarah is saving money to buy a new bike that costs $300. She decides to save her money in two different ways: She saves 1/5 of her weekly allowance and earns additional money by babysitting, which pays her $15 per hour. If Sarah receives a weekly allowance of $50 and she babysits for 4 hours each week, how many weeks will it take her to save enough money to buy the bike? Let's think step by step and output the final answer within \boxed{}.
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