On the same day in $2014,$ two people$--$Abbot in New York, and Costello in Seattle$--$apply for a patent on a new hydrogen$-$powered engine. They worked independently, and then each simply mailed their applications to the Patent and Trademark Office $($PTO$).$ Who will get the patent?

The one who has already sold his designs

The one who had a working model engine first

The one who has plans for a commercial operation

The one whose application arrives first