Simplify first before evaluating. When a=0.25, b=1.25, find the value of 5b-4.6a+5.4ab.
先化简在求值．当a=0.25，b=1.25时，求5b-4.6a+5.4a-b的值．
<gadget id="calculator">4 * 1.25</gadget>
<output>5</output>

<gadget id="calculator">0.8 * 0.25</gadget>
<output>0.2</output>

<gadget id="calculator">5 + 0.2</gadget>
<output>5.2</output>

<result>5.2</result>