Jane is planning to buy fruits for a party. She finds that 3 kilograms of grapes cost 18 yuan, and 5 kilograms of bananas cost 40 yuan. She wants to buy enough fruits so that the total cost is the same for both types of fruits. How many kilograms of each type should she buy to keep the costs equal? Let's think step by step and output the final answer within \boxed{}.
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