Answer: 2*10^-3 nC
Explanation: The capacitor of two plates is given by C= εoA/d where A and d , are the area and the separation of the plates, respectively.
We also know that C=Q/V and V=E*d ( E=electric field between the plates)
From the above expression we have:
Q= εo*A*E= 8.85 ^10-12*7.54 * 10^-4*300= 2*10^-3 nC
