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}

{Φ} is a / an

1. empty set
2. infinite set
3. singleton set
4. universal set

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)

Fill in the blanks :

(i) In a …………… form, we list the properties satisfied by each element of the set.

(ii) A void set is usually denoted by …………… .

(iii) If A ⊆ X, then X is called a …………… of A.

(iv) Two finite sets having the same number of elements are said to be …………… .

(v) n(A ∪ B) + n(A ∩ B) = …………… .