So if I'm correct
There are 5,280 feet in a mile
And since an hour has 60 minutes and each minute has 60 seconds. You would multiply 5,280 by 55 which is the miles. And then multiply 60 by 60 because there are 60 minutes in an hour and 60 seconds in a minute. Then divide 290, 400 / 3, 600. Because to find speed you divide distance over time. And the answer is 80.67 feet per second.
Hope this helps!