Two 1.50cm -diameter disks spaced 1.80mm apart form a parallel-plate capacitor. The electric field between the disks is 5.10×10^5 V/m

Question

I got the voltage as =918

but

B. How much charge is on each disk?
_________C?
and

C. An electron is launched from the negative plate. It strikes the positive plate at a speed of 2.50×107m/s . What was the electron's speed as it left the negative plate?
______ m/s?

thank you so much guys!!