1. The problem statement, all variables and given/known data The electric potential V in a region of space is given by the following expression, where A is a constant. V(x, y, z) = A (6x^2 - 7y^4 + 6z^2) (a) Derive an expression for the electric field vector E at any point in this region. (Use the following as necessary: A, x, y, and z.) x-component Ex = -12Ax y-component Ey = 28Ay^3 z-component Ez = -12Az (b) The work done by the field when a 2.50 µC test charge moves from the point (x, y, z) = (0, 0, 0.380 m) to the origin is measured to be 4.00 10-5 J. Determine A. A = 18.47 (c) Determine the electric field at the point (0, 0, 0.380). E(0, 0, 0.380) = 82.4 N/C negative z (d) What is the radius of the equipotential contour corresponding to V = 1150 V and y = 9.00 m? r =????? 2. Relevant equations 3. The attempt at a solution All I need is part (d). I have no idea what it is talking about.