function wc_update_240_shipping_methods() {
	/**
	 * Flat Rate Shipping.
	 * Update legacy options to new math based options.
	 */
	$shipping_methods = array(
		'woocommerce_flat_rates'                        => new WC_Shipping_Legacy_Flat_Rate(),
		'woocommerce_international_delivery_flat_rates' => new WC_Shipping_Legacy_International_Delivery(),
	);
	foreach ( $shipping_methods as $flat_rate_option_key => $shipping_method ) {
		// Stop this running more than once if routine is repeated.
		if ( version_compare( $shipping_method->get_option( 'version', 0 ), '2.4.0', '<' ) ) {
			$shipping_classes  = WC()->shipping()->get_shipping_classes();
			$has_classes       = count( $shipping_classes ) > 0;
			$cost_key          = $has_classes ? 'no_class_cost' : 'cost';
			$min_fee           = $shipping_method->get_option( 'minimum_fee' );
			$math_cost_strings = array(
				'cost'          => array(),
				'no_class_cost' => array(),
			);

			$math_cost_strings[ $cost_key ][] = $shipping_method->get_option( 'cost' );
			$fee                              = $shipping_method->get_option( 'fee' );

			if ( $fee ) {
				$math_cost_strings[ $cost_key ][] = strstr( $fee, '%' ) ? '[fee percent="' . str_replace( '%', '', $fee ) . '" min="' . esc_attr( $min_fee ) . '"]' : $fee;
			}

			foreach ( $shipping_classes as $shipping_class ) {
				$rate_key                       = 'class_cost_' . $shipping_class->slug;
				$math_cost_strings[ $rate_key ] = $math_cost_strings['no_class_cost'];
			}

			$flat_rates = array_filter( (array) get_option( $flat_rate_option_key, array() ) );

			if ( $flat_rates ) {
				foreach ( $flat_rates as $shipping_class => $rate ) {
					$rate_key = 'class_cost_' . $shipping_class;
					if ( $rate['cost'] || $rate['fee'] ) {
						$math_cost_strings[ $rate_key ][] = $rate['cost'];
						$math_cost_strings[ $rate_key ][] = strstr( $rate['fee'], '%' ) ? '[fee percent="' . str_replace( '%', '', $rate['fee'] ) . '" min="' . esc_attr( $min_fee ) . '"]' : $rate['fee'];
					}
				}
			}

			if ( 'item' === $shipping_method->type ) {
				foreach ( $math_cost_strings as $key => $math_cost_string ) {
					$math_cost_strings[ $key ] = array_filter( array_map( 'trim', $math_cost_strings[ $key ] ) );
					if ( ! empty( $math_cost_strings[ $key ] ) ) {
						$last_key                                = max( 0, count( $math_cost_strings[ $key ] ) - 1 );
						$math_cost_strings[ $key ][0]            = '( ' . $math_cost_strings[ $key ][0];
						$math_cost_strings[ $key ][ $last_key ] .= ' ) * [qty]';
					}
				}
			}

			$math_cost_strings['cost'][] = $shipping_method->get_option( 'cost_per_order' );

			// Save settings.
			foreach ( $math_cost_strings as $option_id => $math_cost_string ) {
				$shipping_method->settings[ $option_id ] = implode( ' + ', array_filter( $math_cost_string ) );
			}

			$shipping_method->settings['version'] = '2.4.0';
			$shipping_method->settings['type']    = 'item' === $shipping_method->settings['type'] ? 'class' : $shipping_method->settings['type'];

			update_option( $shipping_method->plugin_id . $shipping_method->id . '_settings', $shipping_method->settings );
		}
	}
}