jQuery script - Field based on quantity input

I am trying to display a value based on woocommerce quantity input and i'm using the following jQuery script.

jQuery(function($){
    var form = 'form.variations_form',       selected = 'input[name="variation_id"]',
    attrVal = 'input#attr-hidden';

    var price = <?php echo $product->get_price(); ?>;
    $(form).on( 'blur', 'select', function() {
        if($(selected).val() != ''){
            if(($(attrVal).val() == 'Black') && ($('[name=quantity]').val() >= 1 && $('[name=quantity]').val() <= 50)){
                print_price = '15'
            }
            if(($(attrVal).val() == 'Black') && ($('[name=quantity]').val() >= 51 && $('[name=quantity]').val() <= 100)){ 
                print_price = '10'
            }
        }
    });

    var currency = '<?php echo get_woocommerce_currency_symbol(); ?>';

    $('[name=quantity]').change(function(){
        if (!(this.value < 0)) {
            var print_product_total = parseFloat(print_price * this.value);

            $('#print_total_price .print_price').html( currency + print_product_total.toFixed(2));
        }
        $('#print_total_price').toggle(!(this.value <= 0));
    });
});

Code (JavaScript):

What this script does is that if selected attribute of a product is "Black" and quantity input is greater that 1 and less that 50 is displays a field with value "15" and if it is greter that 51 and less than 100 it displays "10".

The problem is that if i enter quantity 1 and then changed it to 51 it still displays "15" unless i select again the attribute "Black".

 

I'd have to see the markup being manipulated, but this looks like the typical train wreck laundry list of how NOT to use JavaScript so typical of jQuery.

I'm really wondering though why you're waiting for blur instead of "change".