If the regular set $$A$$ is represented by $$A = {\left( {01 + 1} \right)^ * }$$ and the regular set $$'B'$$ is represented by $$B = \left( {{{\left( {01} \right)}^ * }{1^ * }} \right),$$ which of the following is true?

How many substrings of different lengths (non-zero) can be formed from a character string of length $$n$$ ?

$$\sum { = \left\{ {a,b} \right\},\,\,} $$ which one of the following sets is not countable.

Which two of the following four regular expressions are equivalent?
(i) $${\left( {00} \right)^ * }\left( {\varepsilon + 0} \right)$$
(ii) $${\left( {00} \right)^ * }$$
(iii) $${0^ * }$$
(iv) $$0\,\,{\left( {00} \right)^ * }$$