To work out the distance of the path, you need to find out the circumference.
Formula for circumference = pi multiplied by the diameter
So you simply do:
pi multiplied by 1.4 miles
And you should get:
4.39822971503... miles
Simply round the result to an appropriate value (e.g. 3 decimal places).
Answer: 4.398 miles (to 3dp)
Hope the answer helps :)