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.
Analyze the relationship between 'FedEx' and 'FedEx Ground' within the context of the input sentence.
Options: subsidiary, industry, distributed by, chairperson