Let U = {x: x is a natural number and x ≤ 10} A = {a: a is an even natural number and a < 10}
B = {b: b is a prime number and b ≤ 9}
Then AI ∩ BI is ______.
Let ∪ = {x: x is a natural number and x ≤ 10}
A = {a: a is an even number and a < 10}
Then AI ∩ BI is
If set A = {1, 2, 3} and set B = {2, 3, 5, 7}. Then the number of elements in A × B is ___