(a) What is the magnitude of the electric field in a region where the potential is given by the expression V = ax2 + b where a = -200 V/m and b = 175 V? (Substitute numerical values, and express your answer in terms of x. Assume SI units, but do not include units in your answer.) E = V /m2 (b) What is the magnitude of the electric field at x = 8.00 m? V/m