For each of the following four languages, give a dfa that will accept the language. assume ? = {a, b} for first three languages and ? = {0, 1, 9, .} for the fourth language.
a. set of strings whose third last symbol is an a.
b. set of strings with at least 3 a 0 s and number of b 0 s = 3.
c. set of strings which do not contain ab as a substring.
d. fixed-decimal literals with no superfluous leading or trailing zeros. every literal must have at least one digit before and after the decimal point. thus, for example, 0.0, 1.0, 0.1, 123.01, and 123005.0 are legal, but 0, .12, 23., 01.0, 1.000, and 002345.1000 are not. in describing the transitions, you may use d to stand for 0, 1, . . , 9 and nzd to stand for 1, . . , 9.