What is the electric field at the point (3.0 m, 1.0 m) if the electric potential at points in an xy plane is given by v = (3.0 v/m2)x2 - (3.0 v/m2)y2?

a) 20.0 N/C
b) 15.0 N/C
c) 16.5 N/C
d) 18.0 N/C