Consider the following grammar for describing meeting times that can be given by either time values or intervals. The rules for the nonterminal time are not important here; assume that the Haskell type Time represents specific time values. mtg::= at time from time to time Which of the following data type definitions for Mtg are a correct representation of the abstract syntax for the mtg grammar? data Mtg = From Time Time At Time data Mtg = Time | From Time Time data Mtg = At Time | From Time Time data Mtg = From Time Time | At Time Time SABAaAbBbBa Which of the following statements are true for all sentences of L ? All as precede all b's. Each sentence contains one or more a's. Each sentence contains exactly as many a's as b's. Each sentence contains one or more b's. Each sentence contains at least two letters