The Boundary Shown Is That of a Uniform Magnetic Field $\mu$

The boundary shown is that of a uniform magnetic field directed in the positive z direction.An electron enters the magnetic field with a velocity pointing along the x axis and exits 0.63 $\mu$ s later at point A.What is the magnitude of the magnetic field?

A) 18 $\mu$ T
B) 14 $\mu$ T
C) 28 $\mu$ T
D) 34 $\mu$ T
E) 227 $\mu$ T