Can anyone help with the following? I think i have the answer i would just like to verify that it is correct,

Question

An equipotential surface that surrounds a point charge q has a potential of 490 V and an area of 1.1 m2. Determine q

Answer 1

A=4πr² --> r=sqrt(A/4π)
r=sqrt(1.2/4π)= 0.30 m

φ=q/4πε₀r --> q=4πε₀rφ
q=4π(8.85x10^-12)(0.30m)(490V)=1.63x10^-8C