The potential in a region of space due to a charge distribution is given by the expression V = ax2z + bxy − cz2 where a = −4.00 V/m3, b = 2.00 V/m2, and c = 6.00 V/m2. What is the electric field vector at the point (0, −8.00, −8.00) m? Express your answer in vector form.