Given the distance between 7V equipotential and the 5V at point B is .9cm and the distance between the 3V equipotential and the 5V at point B is 1.0cm, what is the magnitude of the electric field at point B?

(A) 2.0 V/cm
(B) 2.2 V/cm
(C) 2.1 V/cm
(D) .5 V/cm