Consider the following sets :

S1. Set of all recursively enumerable languages over the alphabet $\{0,1\}$

S2. Set of all syntactically valid C programs

S3. Set of all languages over the alphabet $\{0,1\}$

S4. Set of all non-regular languages over the alphabet $\{0,1\}$

Which of the above sets are uncountable?

Let $\Sigma$ be the set of all bijections from $\{1, \ldots, 5\}$ to $\{1, \ldots, 5\}$, where id denotes the identity function, i.e. $\operatorname{id}(j)=j, \forall j$. Let $\circ$ denote composition on functions. For a string $x=$ $x_1 x_2 \cdots x_n \in \Sigma^n, n \geq 0$, let $\pi(x)=x_1 \circ x_2 \circ \cdots \circ x_n$. Consider the language $L=\left\{x \in \Sigma^* \mid \pi(x)=i d\right\}$. The minimum number of states in any DFA accepting $L$ is $\qquad$

Ten friends planned to share equally the cost of buying a gift for their teacher. When two of them decided not to contribute, each of the other friends had to pay Rs 150 more. The cost of the gift was Rs. ___________.