WC Measurement Price Calculator customization to hide the product price per unit http://www.woothemes.com/products/measurement-price-calculator/

wc-measurement-price-calculator-hide-prices.php

<?php

// Add the following to the bottom of your current theme's functions.php

add_filter( 'woocommerce_sale_price_html',           'remove_price_per_unit_html', 15, 2 );
add_filter( 'woocommerce_price_html',                'remove_price_per_unit_html', 15, 2 );
add_filter( 'woocommerce_empty_price_html',          'remove_price_per_unit_html', 15, 2 );
add_filter( 'woocommerce_variable_sale_price_html',  'remove_price_per_unit_html', 15, 2 );
add_filter( 'woocommerce_variable_price_html',       'remove_price_per_unit_html', 15, 2 );
add_filter( 'woocommerce_variable_empty_price_html', 'remove_price_per_unit_html', 15, 2 );
add_filter( 'woocommerce_variation_sale_price_html', 'remove_price_per_unit_html', 15, 2 );
add_filter( 'woocommerce_variation_price_html',      'remove_price_per_unit_html', 15, 2 );

function remove_price_per_unit_html( $price_html, $product ) {

	// if this is a product variation, get the parent product which holds the calculator settings
	$_product = $product;
	if ( isset( $product->variation_id ) && $product->variation_id ) { $_product = get_product( $product->id ); }

	if ( class_exists( 'WC_Price_Calculator_Product' ) && WC_Price_Calculator_Product::pricing_per_unit_enabled( $_product ) ) {
		return '';
	}

	return $price_html;
}

where O should save this file? in which folder/path?