Knowing that a=b=4 and c=0.4, what is the value of 2a-bc?
已知a=b=4，c=0.4时，则2a-bc的值是多少．
<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<gadget id="calculator">4 * 0.4</gadget>
<output>1.6</output>

<gadget id="calculator">8 - 1.6</gadget>
<output>6.4</output>

<result>6.4</result>