Physical quantities are measured as 'nu' where n is the magnitude and u is the unit. For example: A boy measured the length of a room as 3 m. Here 3 is the magnitude and m (metre) is the unit. 3 m can also be written as 300 cm.
No. The only European units I know of who were able to sustain that. kind of speed on foot were Foreign Legion-where the standard was 50. km per day. Other infantry units usually come in under 20 miles a day. (and closer to 12-15 miles per day).
I think 3 MPH is considered standard walking speed for an army, so it's probably an OK estimate for average or normal people. There are a lot of Americans who would be challenged to keep moving for a mile, to cover it in 30, 40 or more minutes.