public function getLevelPrice( $desired, $current ) {

		$price_calc = 0;

		if ( $desired > 20 ) {

	    	if ( $current >= 20 ) {

	    		$price_calc = $price_calc + ( ( $desired - $current ) * 0.80 );
	    		$desired = 0;

	    	} else {

	    		$price_calc = $price_calc + ( ( $desired - 20 ) * 0.80 );
	    		$desired = 20;

	    	}

	    }

	    if ( $desired > 10 ) {

	    	if ( $current >= 10 ) {

	    		$price_calc = $price_calc + ( ( $desired - $current ) * 0.65 );
	    		$desired = 0;

	    	} else {

	    		$price_calc = $price_calc + ( ( $desired - 10 ) * 0.65 );
	    		$desired = 10;

	    	}

	    }

	    if ( $desired > 0 ) {

	    	$price_calc = ( $price_calc + ( ( $desired - $current ) * 0.12 ) ) + 0.15;
	    	$desired = 0;

	    }

    	return $price_calc;

	}