Answer:
The first digit of 15,951 did not change in two hours.
Therefore 1 is the first and last digit of the new number.
The second and fourth digits changed to 6.
If the middle digit is 0,1,2, then the vehicle travelled 110, 210, 310 miles in two hours.
The first alternative is the correct choice.
Therfore the automobile travelled at 55 MPH