Amendments:
#6(a) V = (s/6)^(3/2)
#14(b) Only the 2 min pts should be given as answers. [ The 2 pts of inflexion are used for sketching the graph. ]
#15(a) a = 1, b = -3
#15(b) min (2, -4), max (0, 0), inflexion (1, -2)
#16(a) min (1, -1), max (2, -26), inflexion (-0.5, f(-0.5))
