If A = {x : x ∈ N, 5 ≤ x < 10} and B = {1, 2, 3, 4, 5}, then n(A - B) is equal to

1. 1
2. 2
3. 4
4. 5

If X = {x : x is a multiple of 5} and Y = {x : x is a multiple of 7}, then X ∩ Y is

1. Φ
2. {x : x is a multiple of 2}
3. {5, 7}
4. {x : x is a multiple of 35}

If A is any set and U is the universal set, then the complement of A is

1. Φ
2. A
3. U - A
4. U

n(A - B) is equal to

1. n(A) - n(B)
2. n(A) - n(A ∪ B)
3. n(A ∪ B) - n(A ∩ B)
4. n(A) - n(A ∩ B)