An air conditioner of a certain brand in a shopping mall costs 3,000 yuan a unit. Now the price is reduced for promotion. As a result, the sales volume has doubled and the income has increased (7/10). How much is the price cut for an air conditioner?
商场某品牌的空调3000元一台，现在降价促销，结果销量增加了一倍，而收入增加(7/10)，求一台空调降价多少元？
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 + (7/10)</gadget>
<output>17/10 = around 1.7</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3_000 * (17/10) * (1/2)</gadget>
<output>2_550</output>

<gadget id="calculator">3_000 - 2_550</gadget>
<output>450</output>

<result>450</result>