Q = 3.973x10⁻⁷C.
The key to solve this problem is using the equation of a parallel plate capacitor.
C = Q/Vᵃᵇ = ε₀ A/d Where C is the capacitance, Q is the charge placed on the plates, Vᵃᵇ is the potential difference between the plates, ε₀ is the constant of the permittivity of vacuum, A is the area of the plates, and d is the separation of the plates.
Clear Q from the equation Q/Vᵃᵇ = ε₀ A/d:
Q = ε₀AVᵃᵇ/d
With ε₀ = 8.85x10⁻¹²F/m, A = 5.10x10⁻³m², Vᵃᵇ = 125.00V, and d = 1.42x10⁻⁵m
Q = (8.85x10⁻¹²F/m)(5.10x10⁻³m²)(125.00V)/1.42x10⁻⁵m = 3.973x10⁻⁷C
