For demonstration purposes, the transfer operation is modified to roll back the transaction whenever the transfer amount is an even number.

出于演示的目的，我们将转帐操作修改为每当转帐金额是偶数时就回滚事务。

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Small amounts of money can be transferred via PayPal, which does not require a minimum transfer amount, although transactions do incur a charge, currently set at 3.9%.

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You just transfer the amount you need back into your checking account from your savings account and voila!

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The solution IDEO came up with was to introduce a credit card, "Keep The Change, " which would instantly transfer the amount customers would usually round up into a separate savings account.

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