/soy/ - Soyjaks

Can u guys help me with this question?
A capacitor is connected to a voltage source that applies a potential difference 𝑈 = 300 V between the plates. The capacitor is in a vacuum and consists of circular plates with radius 𝑅 = 20 cm, placed a distance 𝑑 = 1.0 mm apart.

a. Calculate the electric field 𝐸 between the plates.

Because of the applied potential difference 𝑈, a charge 𝑄 ends up on one plate and a charge −𝑄 on the other plate. You can show (this is taught at TU/e, among other places) that the electric field is also given by 𝐸 = 4𝜋𝑘𝑄/𝐴, where 𝐴 is the area of the plates.

b. Calculate the charge 𝑄 (in C) on the plates at the applied potential difference 𝑈 = 300 V.

c. What does 𝑄 become if the potential difference is made 𝑈 = 600 V?