3. (10 points) A store bought a batch of greeting cards at 21 cents each, and sold them for a total of 14.57 yuan. If each card was sold at the same price, and the selling price did not exceed twice the purchase price, then the store made a total profit of $\qquad$ cents.

将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。 

Note: The last sentence is a repetition of the instruction and should not be included in the translation. Here is the final version:

3. (10 points) A store bought a batch of greeting cards at 21 cents each, and sold them for a total of 14.57 yuan. If each card was sold at the same price, and the selling price did not exceed twice the purchase price, then the store made a total profit of $\qquad$ cents.
【Analysis】First, convert yuan to fen to make all numbers integers. The number of cards must be an integer, so we can factorize 1457 to find the number that meets the requirements.

【Solution】According to the problem, 14.57 yuan is 1457 fen.
Factorize 1457 into prime factors: $1457=31 \times 47$.
Since the cost price is 21 fen and the selling price does not exceed 42 fen, the selling price is 31 fen for 47 cards,
$$
47 \times (31-21) = 470 \text{ (fen) }
$$

Therefore, the answer is: 470