JSFiddle - React, Tailwind, and code Playground

by CRHosting

HTML

<span class="Amount">
    <select name="Amount" class="wpcf7-form-control  wpcf7-select">
        <option value="$50">$50</option>
        <option value="$75">$75</option>
        <option value="$100">$100</option>
        <option value="$150">$150</option>
        <option value="$300">$300</option>
    </select>
</spa>

<span class="Qty">
    <input type="text" name="Qty" size="2" maxlength="2">
</span>

total:<span input name="total" disabled="true" id="total"> </span>

JavaScript

$('.Qty input').keyup(multiply);
$('span.Amount select').change(multiply);
function multiply() {
    var quantity = parseFloat($('.Qty input').val());

    var dollars = $('span.Amount select').val().substr(1);

    $('#total').text('$'+(quantity * dollars )); 
}