A charged particle is sitting at the point (3,-1,0). An electric field is exerting a force on this particle with magnitude F(x, y, z) = 3x - 2y^2 + xyz.
a) At what instantaneous rate is the magnitude of the force changing when the particle starts moving toward the point (1,2,-1)?
(b) Still assuming the particle is at (3,-1,0), in which direction would it have to move to make the magnitude of the force increase most rapidly? Give your answer as a unit vector.
(c) Suppose the particle is moving along a curve r(t). At some time t = to, the particle has position r(to) = (3,-1,0) and velocity r'(t) = (2,2,1). At what rate is the magnitude of the force on the particle changing with respect to time at t = to?