KEEP AN EYE 
An aircraft carries 521 people safely from Kedarnath to Dehradun in 12 hours.How many rounds it take.
1.It can carry a maximum of 54 people at a time.
2.I 45 minute to fly from one city to other and 15 minute while waiting.
Option:
A.If one alone can give the answer but other can not give answer.
B.If both together can give the answer.
C.If either of two can give the answer
D.Neither of two can give the answer
please tell the solution..