It is known that a=b=4, c=0.4, then what is the value of 2a-5c.
已知a=b=4，c=0.4，那么2a-5c的值是多少．
<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<gadget id="calculator">5 * 0.4</gadget>
<output>2</output>

<gadget id="calculator">8 - 2</gadget>
<output>6</output>

<result>6</result>