Answer:
If johns destination at first when he was covering it in 5 hours of drive was 150 km, then lets say that he finds a short cut that it is about a 100 km in total distance from its initial point and with the speed of 40 km's, while at first 20 km's he will be driving at 20 km's due to a storm. So, now doing the simple math for it we will get the whole results for the problem, which are given as below:
Explanation: