All totaled, our first quarter adjusted operating income increased 56% year-over-year primarily due to international priority volume growth of 31%, a surge in demand for U.S. residential delivery, yield improvement at FedEx Ground and FedEx Freight, a $130 million benefit from an additional operating day, a $65 million benefit from a reduction in aviation excise taxes provided by the Cares Act and a better alignment of our expenses, especially at FedEx Freight.
In the context of the input sentence, determine the relationship between 'FedEx Ground' and 'FedEx'.
Options: owned by, currency, parent organization, founded by