What is the set of values of p for which the point of extremum of the function f(x) = x^3 - 3px^2 + 3(p^2 - 1)x + 1 lies in the interval (-2, 4)?
a) p in (-[infinity], -2) ∪ (2, [infinity])
b) p in (-[infinity], -1) ∪ (1, [infinity])
c) p in (-[infinity], 0) ∪ (0, [infinity])
d) p in (-[infinity], 1) ∪ (1, [infinity])