string counting

Consider the following two regular expressions over the alphabet {0,1} : $$r = 0^* + 1^*$$ $$s = 01^* + 10^*$$ The total number of strings of length less than or equal to 5, which...

Let L 1 be the language represented by the regular expression b * ab * (ab * ab * ) * and L 2 = { w ∈ (a + b) * | |w| ≤ 4 } , where |w| denotes the length of string w . The number...