JSFiddle - React, Tailwind, and code Playground

HTML

<table width="100%" border="0" cellspacing="0" cellpadding="0">
  <tr>
    <td height="60" colspan="5" valign="top"><h2>Variants:</h2></td>
    </tr>
  <tr>
    <td height="40" align="left"><div class="variant">Flowers:</div></td>
    <td height="45" align="right" style="padding-right:14px;"><label>Size<select name="flowers_size" id="flsz" type="text" size="1" class="select2" tabindex="1" ><option selected="selected">200 ML</option></select></label></td>
    <td height="45" align="right" style="padding-right:14px;"><label>Price<input name="flowers_price" type="text" class="input5" id="flpr" tabindex="1" value="MRP 1495.00" readonly="readonly" /></label></td>
    <td height="45" align="right" style="padding-right:14px;"><label>Quantity<select name="flowers_quantity" id="flqt" type="text" size="1" class="select3" tabindex="1" oninput="calculate()">
      <option value="0">0</option>
      <option value="1">1</option>
      <option value="2">2</option>
      <option value="3">3</option>
      <option value="4">4</option>
      <option value="5">5</option>
      <option value="6">6</option>
      <option value="7">7</option>
      <option value="8">8</option>
      <option value="9">9</option>
      <option value="10">10</option>
      <option value="11">11</option>
      <option value="12">12</option>
      <option value="13">13</option>
      <option value="14">14</option>
      <option value="15">15</option>
      <option value="16">16</option>
      <option value="17">17</option>
      <option value="18">18</option>
      <option value="19">19</option>
      <option value="20">20</option>
      <option value="21">21</option>
      <option value="22">22</option>
      <option value="23">23</option>
      <option value="24">24</option>
      <option value="25">25</option>
      <option value="26">26</option>
      <option value="27">27</option>
      <option value="28">28</option>
      <option value="29">29</option>
      <option value="30">30</option>
     ...

JavaScript

function calculate() {
		var flowersSize = 200;
		var flowersPrice = 1495;
		
		var fruitsSize = 200;
		var fruitsPrice = 1295;	
		
		var plantationsSize = 200;
		var plantationsPrice = 1195;	
		
		var vegetablesSize = 200;
		var vegetablesPrice = 995;	
		
		var cerealsSize = 200;
		var cerealsPrice = 895;	
		
		var flowersQuantity = flqt.options[flqt.selectedIndex].value;
		var fruitsQuantity = frqt.options[frqt.selectedIndex].value;
		var plantationsQuantity = plqt.options[plqt.selectedIndex].value;
		var vegetablesQuantity = veqt.options[veqt.selectedIndex].value;
		var cerealsQuantity = ceqt.options[ceqt.selectedIndex].value;
			
		var flowersLitres = flowersSize * flowersQuantity / 1000;
		var fruitsLitres = fruitsSize * fruitsQuantity / 1000;
		var plantationsLitres = plantationsSize * plantationsQuantity / 1000;
		var vegetablesLitres = vegetablesSize * vegetablesQuantity / 1000;
		var cerealsLitres = vegetablesSize * cerealsQuantity / 1000;
		
		flowersLitres = parseFloat(Math.round(flowersLitres * 100) / 100).toFixed(3);
		fruitsLitres = parseFloat(Math.round(fruitsLitres * 100) / 100).toFixed(3);
		plantationsLitres = parseFloat(Math.round(plantationsLitres * 100) / 100).toFixed(3);
		vegetablesLitres = parseFloat(Math.round(vegetablesLitres * 100) / 100).toFixed(3);
		cerealsLitres = parseFloat(Math.round(cerealsLitres * 100) / 100).toFixed(3);
		
		fllt.value = flowersLitres;
		frlt.value = fruitsLitres;
		pllt.value = plantationsLitres;
		velt.value = vegetablesLitres;
		celt.value = cerealsLitres;
		
		var totalAmount = flowersQuantity * flowersPrice + fruitsQuantity * fruitsPrice + plantationsQuantity * plantationsPrice + vegetablesQuantity * vegetablesPrice + cerealsQuantity * cerealsPrice;
		
		totalAmount = parseFloat(Math.round(totalAmount * 100) / 100).toFixed(2);
		
		tamt.value = "MRP"+" "+totalAmount.toString().replace(/,/g, "").replace(/\B(?=(\d{3})+(?!\d))/g, ",");
	}