Determine the turning points of f(x)=x³ - 6x² + 1 and their nature.
a. x = 0 (maximum) and x = 4 (minimum)
b. x = 2 (minimum)
c. x = 0 (minimum) and x = 4 (maximum)
d. x = 0 (maximum) and x=1,33 (minimum)