If the number of elements in a set $A$ is $n(A) = 40$,$n(B) = 26$,and $n(A \cap B) = 16$,then what is the value of $n(A \cup B)$?

Which of the following sets is infinite?

Which of the following sets is finite?

In a certain class,$72 \%$ of the students took Biology and $44 \%$ took Mathematics. If each student took at least one of Biology or Mathematics and $40$ students took both of these subjects,the total number of students in the class is:

If $A = \{a, b\}$,$B = \{2, 3, 5, 6, 7\}$ and $C = \{5, 6, 7, 8, 9\}$,find $A \times (B \cap C)$.

For $\theta > \frac{\pi}{3}$,the value of $f(\theta) = \sec^2 \theta + \cos^2 \theta$ always lies in the interval