A regular grammar is a grammar G = (V, T, S, P) in which production rules are of the form A ? a or A ? aB, where a ? T and A, B ? V . The rule S ? ? is allowed, where S is the start variable. Regular grammars generate regular languages. Give a regular grammar for the following regular languages:

L1 = L(a ? b ? + (a + b)(a + b))

L2 = {w ? {a, b} ? : |w| = 3k, for some k ? 0}