A car started from city A towards city B and travelled a certain distance at its usual speed. It then developed an engine problem, because of which its speed decreased by 10% for the remaining distance and it arrived at its destination one hour later than expected. Had the engine problem developed after it had travelled 20% more distance, it would have arrived at its destination ten minutes sooner than it actually did. How long did the car travel before the engine developed the problem?Solution plzzz......

1) 6 hours
2) 7.5 hours
3) 4.5 hours
4) 9 hours