$M$ is older than $R$. $Q$ is younger than $R$ and $N$. $N$ is not as old as $M$. Who among $M, N, R$,and $Q$ is the oldest?

How many $3$s are there in the following number sequence which are immediately preceded by $6$ but not immediately followed by $7$?
$2, 3, 7, 4, 3, 5, 6, 3, 7, 4, 6, 3, 8, 9, 6, 5, 1, 8, 3, 7, 2, 4, 2, 8, 6, 3, 9$

In a class of $40$ students,Samir's rank from the top is $12^{th}$. Alok is $8$ ranks below Samir. What is Alok's rank from the bottom?

In a row of girls, Rita and Monika occupy the ninth place from the right end and tenth place from the left end, respectively. If they interchange their places, then Rita and Monika occupy the eighteenth place from the left end. How many girls are there in the row?

In a row of children facing North,Ritesh is $12^{th}$ from the left end. Sudhir,who is $22^{nd}$ from the right end,is $4^{th}$ to the right of Ritesh. How many children are there in the row in total?

$(I)$ Kamal is available at home from $12$ noon to $4 \,p.m.$ on Tuesday,Thursday,and Sunday.
$(II)$ His younger brother Navin is available at home on Monday,Thursday,Friday,and Sunday between $10 \,a.m.$ to $2 \,p.m.$
$(III)$ The eldest brother Rajiv is available between $9 \,a.m.$ to $12$ noon on Monday,Wednesday,and Thursday and $2 \,p.m.$ to $4 \,p.m.$ on Friday,Saturday,and Sunday.
On which day$(s)$ of a week,the youngest and the eldest brothers are available at home at the same time?