physics help!
posted by UnKnown .
An electron enters the region of a uniform electric field between two oppositely charged parallel plates as shown, with an initial velocity of 3 x 106 m/s. The electric field between the plates is measured to be E = 200N/C. The horizontal length of the plates is 10cm.
a. Find the acceleration of the electron while it is in the electric field.
b. How long does it take the electron to travel the length of the plates and
leave the field?

a. Acceleration is
a = e*E/m
e is the electron charge and m is the electron mass
b. Solve the equation
Since the electron's velocity component parallel to the plates remains the same as when it entered,
t = 0.10 m/(3*10^6 m/s) 
how do we find out the electron charge and mass if we don't know what type it is?