JSFiddle - React, Tailwind, and code Playground

HTML

<form name="frm">
    <input id="a" name="value1" onblur="calc()">
    <select id="b" name="value2" onchange="calc()">
        <option value="0.001">.001</option>
        <option value="0.005">.005</option>
        <option value="0.01">.01</option>
    </select>
    <input id="c" name="value3" >
    <span id="revenue1"></span> <input type="button" value="calculate" onclick="calc()">
</form>

JavaScript

function calc() {
var a=parseFloat($("form[name=frm] #a").val());
var b=parseFloat($("form[name=frm] #b").val());
var c=parseFloat($("form[name=frm] #c").val());
   var d = (a*b*c);
    //$("#revenue1").text(d);
    var revenue = (d<c)?0:d;
   if(!isNaN(d))
    $("#revenue1").text("$" + revenue);

}