2. Describe a CFG for the following languages: (a) (we(0.1)' I w= rev(w)} Note: w denotes flipping every bit in the string w, for example: 00101 11010. (b) (w {a, b)' I num(a, w)-num(b, w)) Hint: Consider the following example where we graph num(a, w) num(b. w) for all prefixes of w: 0 -1 Imagine breaking up the string into pieces every time the graph crosses the x-axis. Look at the first and last character of each such piece and think recursively