=3√a×b×c=3⇒a×b×c=27⇒3√d×e×f⇒d×e×f=64The least arithmetic mean M is obtained when a = b = c = 3 and d = e = f = 4.
Therefore, the least value of M
Also, M ≠ 3.5 as at least three elements among a, b, c, d, e, f are distinct, which will give the value of M greater than M (one such set is a = 3, b = 3, c = 3, d = 2, e = 4, f = 8).
∴M>3.5