Update my answer to Exercise 3.31.

Modified is the following file:

	Exercise_3.31.tm

Thank you!
							Lawrence X. Amlord
							  Oct 21st, 2013
							  Xi'an, China
Update my answer to Exercise 3.31.

Modified is the following file:

	Exercise_3.31.tm

Thank you!
							Lawrence X. Amlord
							  Oct 21st, 2013
							  Xi'an, China