Answer:
\$(0|[1-9][0-9]*)(\.[0-9][0-9])?
\$(0|[1-9][0-9]*)(\.[0-9][0-9])?
The automaton that corresponds to this RE.
The '.' character is escaped because we want to match '.' and not any character.
The dollar sign is escaped \$ becase it also
has a special meaning in regular expressions,
not yet discussed.
Write a RE that matches strings that start with an 'a' and end with a 'b' and have any number of a's and b's in the middle.