1. [10 points] Suppose that over a certain region of space the electrical potential V is given by V(x, y, z) = 5x4-3xy+xyz. (a) Find the rate of change of the potential at P(1.2,3) in the direction of the vector u=2i-j+k. (b) In which direction does V change most rapidly at P? (c) Find the maximum rate of change at P