An electron enters the region between two uniformly charged horizontal plates of opposite signs. Its initial velocity, halfway between the plates (Figure 2.68), is 2 10^6 i m/s. The plates are 4 cm long and 1.6 cm apart. It is considered that, in the whole region between the plates, the electric field is uniform and perpendicular to the plates. (a) What is the maximum modulus that the vertical electric field can have so that the electron does not touch any of the plates? (b) From the result obtained in (a), draw the graph of the trajectory of the electron for x ranging from 0 to 4 cm.