(a) Let E = { a, b } . Write regular expressions for the following statements. 1. All strings of a's and b's in which the total number of a's is divisible by three. 2. All strings of a's and b's that...

(Subject: Compiler Concepts)

Extracted text: (a) Let E = { a, b } . Write regular expressions for the following statements. 1. All strings of a's and b's in which the total number of a's is divisible by three. 2. All strings of a's and b's that contains exactly three b's. 3. All strings of a's and b's that at some point contain the substring bbb. 4. All strings of a's and b's that have at least one a and at least one b.