# If $A=\{x:x\in R\:\:and\:\:x\geq 4\}$ and $B=\{x:x\in R\:and\:x< 5\}$, then $A\cap B$ = ?

(A) $(4,5]$
(B) $(4,5)$
(C) $[4,5)$
(D) $[4,5]$

Ans: $[4,5)$
Because, if $\geq\:\:or\:\:\leq$ comes then use closed bracket [ ].
If < or > comes then use open bracket ( ).