7. Let L = (x E (a, b)' | Na (x)-Nb(x)) where Nc(x) denotes the number of c's in x. A grammar for L with start symbol E can be written as E aEbEbEaEIA. With this grammar, we can construct a grammar for the following language L1-xE la, b)* I Na(x) > N, (x)) as However, s EaES | is not a grammar for L1. In the following blank, give a string that cannot be generated by the first grammar (S EaET T--aETI ), but can be generated by the second one (S--EaES | ). (1 point)