The second bus departs from Newton to Oldville at 9:55 and reaches at 11:05. It means that it took 1 hour and 10 mins to reach Oldville.
The next available bus from Oldville to Newton is at 15:35. This means that Su-Lin is in Oldville for 4 hours and 30 minutes.
The bus then leaves at 15:35 and arrives at Newtown at 16:45. This suggests that it took 1 hour and 10 mins to go back.
Total time = 1 hour and 10 mins + 4 hours and 30 minutes + 1 hour and 10 mins
