Give regular expressions such that could be used with grep

Question

UNIX (Mac linux)

Give regular expressions (such that could be used with grep and egrep) for each of the following:

1. All lines beginning with the phrase 'Unix is ' (both words together)
2. All lines that end in either 'a', 'b', or 'c'
3. All lines that contain the word 'result' followed by any three numbers
4. All lines that contain either 0 or 1 instances of the character 'x', but no more
5. All lines that contain a word with 0 or more of the letter 'a', followed by 1 or
6. more of the letter 'b', followed by 0 or 1 letter 'c'