Language $L_{1}$ is defined by the grammar: $S_{1} \rightarrow a S_{1} b \mid \varepsilon$
Language $L_{2}$ is defined by the grammar: $S_{2} \rightarrow a b S_{2} \mid \varepsilon$
Consider the following statements:
- P: $L_{1}$ is regular
- Q: $L_{2}$ is regular
Which one of the following is TRUE?
- Both $P$ and $Q$ are true.
- $P$ is true and $Q$ is false.
- $P$ is false and $Q$ is true.
- Both $P$ and $Q$ are false.