public function fee( $atts ) {
		$atts = shortcode_atts(
			array(
				'percent' => '',
				'min_fee' => '',
			),
			$atts,
			'fee'
		);

		$calculated_fee = 0;

		if ( $atts['percent'] ) {
			$calculated_fee = $this->fee_cost * ( floatval( $atts['percent'] ) / 100 );
		}

		if ( $atts['min_fee'] && $calculated_fee < $atts['min_fee'] ) {
			$calculated_fee = $atts['min_fee'];
		}

		return $calculated_fee;
	}