A person running at a speed of 4 m/s in a circular track of radius 420 m. If he decrease his speed by 1/4 after completing every one round of track, then what is the time take by him to complete two rounds of the track?
1
1.54 hours
2
1540 seconds
3
1540 minutes
4
1.5 hours 40 minutes
5
None of these