Union
$$A \cup B =$$
{ avoiding, earth, fire, getting, ruling, socially useful, void, water, wind }
Symmetric Difference
$$A \ominus B =$$
{ avoiding, earth, fire, getting, ruling, socially useful, void, water, wind }
Difference
$$A - B =$$
{ avoiding, getting, ruling, socially useful }
Difference
$$B - A =$$
{ earth, fire, void, water, wind }
Cartesian Product
$$A \times B =$$
{ (avoiding, earth),
(avoiding, fire),
(avoiding, void),
(avoiding, water),
(avoiding, wind),
(getting, earth),
(getting, fire),
(getting, void),
(getting, water),
(getting, wind),
(ruling, earth),
(ruling, fire),
(ruling, void),
(ruling, water),
(ruling, wind),
(socially useful, earth),
(socially useful, fire),
(socially useful, void),
(socially useful, water),
(socially useful, wind) }
Four temperaments