Answer
The particle still spends $~~130~ns~~$ in the magnetic field during this trip.
Work Step by Step
We can write the equation for the period of motion:
$T = \frac{2\pi~m}{q~B}$
Note that the period does not depend on the speed of the particle.
Therefore, changing the kinetic energy by changing the speed does not affect the period.
The particle still spends $~~130~ns~~$ in the magnetic field during this trip.
