JSFiddle - React, Tailwind, and code Playground

HTML

<form class="form-horizontal text-left" id="meishi">
  <div class="form-group">
    <div class="col-lg-2 topic">
      <label>Design</label>
    </div>
    <div class="col-lg-3">
      <label class="radio-inline">
        <input type="radio" data-drop-a="2160" data-drop-b="2484" data-drop-c="2808" name="design" value="10800">op1
      </label>
    </div>
    <div class="col-lg-4">
      <label class="radio-inline">
        <input type="radio" data-drop-a="2808" data-drop-b="3132" data-drop-c="3456" name="design" value="14040">op2
      </label>
    </div>
    <div class="col-lg-3">
      <label class="radio-inline">
        <input type="radio" data-drop-a="3240" data-drop-b="3564" data-drop-c="3888" name="design" value="16200">op3
      </label>
    </div>
  </div>
  <div class="form-group">
    <label class="col-lg-2" for="qtt">Quantity</label>
    <select id="qtt" class="col-lg-3" name="qtt">
      <option value="">Choose one</option>
      <option value="a">100</option>
      <option value="b">200</option>
      <option value="c">300</option>
    </select>
  </div>
</form>
<br />
subRadio: <span id="subRadio"></span><br />
subDrop: <span id="subDrop"></span><br />
total: <span id="total"></span><br />

JavaScript

$(document).ready(function(){
  $("input[name=design], #qtt").on('change',function(){
    var design = $('input[name=design]:checked');
    var designVal = parseInt(design.val());
    var qtt = $("#qtt").val();
    var subDrop=parseInt(design.data('drop-'+qtt));
    if (!subDrop) subDrop=0;
    if (!designVal) designVal=0;
    $('#subRadio').text(designVal)
    $('#subDrop').text(subDrop)
    $('#total').text(designVal+subDrop)
  });
});