Question 64
Find all real numbers $x$, $y$, $z$, $t \in [0, \infty)$ so that
$$
x + y + z \le t, \quad x^2 + y^2 + z^2 \ge t \text{ and } x^3 + y^3 + z^3 \le t.
$$
$$
x + y + z \le t, \quad x^2 + y^2 + z^2 \ge t \text{ and } x^3 + y^3 + z^3 \le t.
$$