Using the matrices A and B below, what condition must be satisfied in order that AB and BA are defined? 
and 
Definitions:
Nirvana
The ultimate goal in Buddhism, representing a state of enlightenment and liberation from the continuous cycle of birth, death, and rebirth.
Existentialism
The approach to philosophy that focuses on conscious experience (phenomenology), free will, the meaning of life, and other basic questions of existence.
Sartre
Jean-Paul Sartre, a French existentialist philosopher, playwright, and novelist known for his exploration of freedom, existentialism, and the human condition.
Nietzsche
A German philosopher known for his exploration of individual morality, the will to power, and the critique of religion.
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