In 4a+5b, when a=1.2, b=3.8, what is the value of 4a+5b.
在4a+5b中，当a=1.2，b=3.8时，4a+5b的值是多少．
<gadget id="calculator">4 * 1.2</gadget>
<output>4.8</output>

<gadget id="calculator">5 * 3.8</gadget>
<output>19</output>

<gadget id="calculator">4.8 + 19</gadget>
<output>23.8</output>

<result>23.8</result>