Question 12597
Notingwrong with ur quantitative skills but u lack in comprehension skills and need to work on these. 

Yes the time taken by B shall be 2.5 hrs but the tota time in the process is 2.5 + 0.5 Hrs. as the whole thing statted at 8 am, B would catch up with A at 2.5 hrs of his starting which happened 0.5 hrs after A (i.e. 8 am)

hence the answer 11 am