clothing store sells 50 pieces of sportswear in the morning and 20 pieces in the afternoon, and each piece of sportswear is 78 yuan. According to this calculation, how much less is the sale in the afternoon than in the morning? (answer in different ways)
一个服装店上午卖出50件运动服，下午卖出20件，每件运动服78元．照这样计算，下午比上午少卖多少元？(用不同方法解答)
<gadget id="calculator">50 * 78</gadget>
<output>3_900</output>

<gadget id="calculator">20 * 78</gadget>
<output>1_560</output>

<gadget id="calculator">3_900 - 1_560</gadget>
<output>2_340</output>

<result>2_340</result>