If $n(A) = 4$,$n(B) = 3$,and $n(A \times B \times C) = 24$,then find $n(C)$.

Make correct statements by filling in the symbols $\subset$ or $\not\subset$ in the blank spaces:
${2,3,4} \dots {1,2,3,4,5}$

If ${N_a} = \{an : n \in N\}$,then ${N_5} \cap {N_7} = $

Show that the following four conditions are equivalent:
$(i) A \subset B, \quad (ii) A - B = \phi, \quad (iii) A \cup B = B, \quad (iv) A \cap B = A$

State whether the following set is finite or infinite:
The set of circles passing through the origin $(0,0)$.

Write the following set in roster form:
$D = \{ x : x \text{ is a prime number which is a divisor of } 60 \}$