Aunt Wang sold 45 sets of postcards yesterday, with 12 postcards in each set and 3 yuan each. How much did these postcards cost in total?
王阿姨昨天卖出45套明信片，每套明信片12张，每张3元，这些明信片一共卖了多少钱？
<gadget id="calculator">12 * 45</gadget>
<output>540</output>

<gadget id="calculator">3 * 540</gadget>
<output>1_620</output>

<result>1_620</result>