Union
$$A \cup B =$$
{ action, contemplation, enclosure, hearth, maintenance, mound, precontemplation, preparation, roof, termination }
Symmetric Difference
$$A \ominus B =$$
{ action, contemplation, enclosure, hearth, maintenance, mound, precontemplation, preparation, roof, termination }
Difference
$$A - B =$$
{ action, contemplation, maintenance, precontemplation, preparation, termination }
Cartesian Product
$$A \times B =$$
{ (action, enclosure),
(action, hearth),
(action, mound),
(action, roof),
(contemplation, enclosure),
(contemplation, hearth),
(contemplation, mound),
(contemplation, roof),
(maintenance, enclosure),
(maintenance, hearth),
(maintenance, mound),
(maintenance, roof),
(precontemplation, enclosure),
(precontemplation, hearth),
(precontemplation, mound),
(precontemplation, roof),
(preparation, enclosure),
(preparation, hearth),
(preparation, mound),
(preparation, roof),
(termination, enclosure),
(termination, hearth),
(termination, mound),
(termination, roof) }
Transtheoretical model