Let ? = {0, 1}. Write CFGs that generate the following languages:
? {W | W contains no more than three 1's}
? {W | W starts and ends with different symbols}
? {W | W starts with a 1 and has an even length}
? {W | The length of w is even and its middle two symbols are 01}
? {W | W contains twice the number of 0's than 1's}