Answer:
2 x 10⁻¹²F
Step-by-step explanation:
Capacitance is defined as the ration of charge (q) on either plates to the potential difference V between them.
C =

Where q is the charge on the plates
V is the potential difference
From the given parameters:
Charge on plate, q = 2.0 x 10⁻¹⁰C
Potential difference across the plate = 100V
Unknown parameter:
Capacitance of the system = ? = C
Solution
Capacitance = 2.0 x 10⁻¹⁰/100 = 2 x 10⁻¹²F