$L, M$ and $N$ are waiting in a queue meant for children to enter the zoo. There are $5$ children between $L$ and $M$, and $8$ children between $M$ and $N$. If there are $3$ children ahead of $N$ and $21$ children behind $L$, then what is the minimum number of children in the queue?
- $28$
- $27$
- $41$
- $40$