Q52

Let $L_{1}$ be the language represented by the regular expression $b^{*} a b^{*}\left(a b^{*} a b^{*}\right)^{*}$ and $L_{2}=\left\{w \in(a+b)^{*}|| w \mid \leq 4\right\}$, where $|w|$ denotes the length of string $w$. The number of strings in $L_{2}$ which are also in $L_{1}$ is _________.