If n(A) = 3, n(B) = 4, ten write n (A × A × B).
We know ,n(A×B)=n(A)×n(B)
Similarly, n(A×B×C)=n(A)×n(B)×n(C)
Here, n(A)=3 and n(B)=4
n(A×A×C)=n(A)×n(A)×n(B)
=3×3×4
=36