Answer:
6.5454 m
Explanation:
Let the distance from the wire carrying 3 A current is x
Then the distance from the the carrying current 8 A is 24-x
We know that magnetic field due to long wire is given by
It is given that magnetic field is zero at some distance so

Here
So 
Speed = wavelength × frequency
speed = 10/1000 × 5.0
speed = 0.001 × 5.0
speed = 0.005m/s
given that acceleration due to gravity is g = 10 m/s^2
speed of the rocket will reach to 0.9c

now by kinematics



Part b)
distance traveled by it in above time



so this is the distance covered by the object