Answer: 10
Explanation:
n(A × B) represents the number of elements of set A × B, the cartesian product of set A and set B.
Note that the number of elements of the cartesian product of two sets is the product of the number of elements of each of the two sets.
In the problem, n(A × B) is equal to the product of the number of elements of set A and number of elements of set B. Since the number of elements in set A is 5 and the number of elements in set B is 2,
n(A × B) = 5 × 2 = 10
