Find the cardinal number of the sets: $A=\left\{1,2,2,1,3\right\}$.

Find the cardinal number of the set: The set of all Indians having $8$ legs.

Find the cardinal number of the set: The set of all letters in the word $\mathrm{PRINCIPAL}$.

Find the cardinal number of the set: The set of all vowels in the word $\mathrm{PRINCIPAL}$.

State whether the given statement is true or false. Justify your answer.

$37\notin \left\{x:x \mathrm{has} \mathrm{exactly} \mathrm{two} \mathrm{positive} \mathrm{factors}\right\}$

State whether the given statement is true or false. Justify your answer.

$35\in \left\{x:x \mathrm{has} \mathrm{exactly} \mathrm{four} \mathrm{positive} \mathrm{factors}\right\}$