The original price of the computer in the mall is 4,200 yuan. After the 20% discount for the start-of-school promotion, if you have a membership card, you can also reduce the price by 10%. How much does it cost Mr. Wang to buy this computer with the membership card?
商场上的电脑原价4200元，开学促销打了八折后，如果有会员卡还可以减价10%，王老师用会员卡购买这台电脑要多少元？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">4_200 * (4/5) * (9/10)</gadget>
<output>3_024</output>

<result>3_024</result>