1. Where P={c st, dog, bird } and Q={ hot, cold, wet }, define PQ. \{cat hot, dog cold, bird wet\} \{cat, dog, bird, hot, cold, wet\} \{cat, dog, bird, hot, cold, wet, hot, cold, wet, cat, dog, bird\} 2. Define A0. A (1) AA AtA. 3. The regular expression for binary strings of length zero is: 1 point u 4. Which of the following statements are true? Select all that apply. 1 point None of these are commutative nor associative Union is associative Union is commutative Concatenation is associative Concatenation is commutative