I am thinking that maybe the problem is not with the calibration. It might be that the buffered solution is already expired since at this point the solution is already not stable and will give a different pH reading than what is expected.
Answer:
Part a)
distance = 112 miles
Part b)
current position = 112 miles from the position of town
Explanation:
Part a)
Since the distance marker is showing the distance between the town and the position of john at all time
so here we have

Part b)
Current position of John is given as

from the position of the town
Answer:
8672
Explanation:
multiply the length value by 100