Answer:
The time taken by missile's clock is 
Solution:
As per the question:
Speed of the missile, 
Now,
If 'T' be the time of the frame at rest then the dilated time as per the question is given as:
T' = T + 1
Now, using the time dilation eqn:




(1)
Using binomial theorem in the above eqn:
We know that:

Thus eqn (1) becomes:


Now, putting appropriate values in the above eqn:


Explanation:
(4566 m / 4 min) × (1 km / 1000 m) × (60 min / h) = 68.49 km/h
Blood pressure is greater in feet because of gravity