Union
$$A \cup B =$$
{ action, contemplation, earth, fire, maintenance, metal, precontemplation, preparation, termination, water, wood }
Symmetric Difference
$$A \ominus B =$$
{ action, contemplation, earth, fire, maintenance, metal, precontemplation, preparation, termination, water, wood }
Cartesian Product
$$A \times B =$$
{ (action, earth),
(action, fire),
(action, metal),
(action, water),
(action, wood),
(contemplation, earth),
(contemplation, fire),
(contemplation, metal),
(contemplation, water),
(contemplation, wood),
(maintenance, earth),
(maintenance, fire),
(maintenance, metal),
(maintenance, water),
(maintenance, wood),
(precontemplation, earth),
(precontemplation, fire),
(precontemplation, metal),
(precontemplation, water),
(precontemplation, wood),
(preparation, earth),
(preparation, fire),
(preparation, metal),
(preparation, water),
(preparation, wood),
(termination, earth),
(termination, fire),
(termination, metal),
(termination, water),
(termination, wood) }
Transtheoretical model