2. Write down the extended regular expression for following questions. E.g. Social security number in the format of 999-99-9999. Answer: [09]{3}[09]{2}[09]{4} 1) Valid URL beginning with "http://" and ending with ".edu" (e.g. http://cs.gsu.edu, http://gsu.edu ) 2) Non-negative integers. (e.g. 0,+1,3320) 3) A valid absolute pathname in Unix (e.g. /home/ylong4, /test/try.c) 4) Identifiers which can be between 1 and 10 charalcter long, must starting with a letter or an underscore. The following characters can be letters or underscores or digits. (e.g. number,_name1, isOK). 5) Phone number in any of the following format: 9999999999,999 9999999, (999)-999-9999. (Note: all of these formats should be matched by a single regular expression)