Answer:
E = 3.45*10^-19 N/C
Step-by-step explanation:
a) The electric field between two parallel plates id given by the following formula:
(1)
where:
σ: surface charge density of the plates = 39.0nC/m^2
εo: dielectric permittivity of vacuum = 8.85*10^-12 C/Nm^2
You replace these values in the equation (1):

The electric field in between the parallel plates is 3.45*10^-19 N/C