Lele bought a set of "Harry Potter" with the membership card, 36 copies in each set, 28 yuan each, but only spent 900 yuan. How much money has he saved using his loyalty card?
乐乐用会员卡买了一套《哈利•波特》，每套36本，每本28元，但只用了900元．他使用会员卡节省了多少钱？
<gadget id="calculator">28 * 36</gadget>
<output>1_008</output>

<gadget id="calculator">1_008 - 900</gadget>
<output>108</output>

<result>108</result>