Update my answer to Exercise 2.81.

Modified are the following 2 files:

	Exercise_2.81.pdf
	Exercise_2.81.tm

Thank you!
							Lawrence R. Amlord
							   Aug 14th, 2013
							   Fuzhou, China
Update my answer to Exercise 2.82.

Modified are the following 2 files:

	Exercise_2.82.pdf
	Exercise_2.82.tm

Thank you!
							Lawrence R. Amlord
							   Aug 15th, 2013
							   Fuzhou, China
Update my answer to Exercise 2.83.

Modified is the following file:

	Exercise_2.83.scm

Thank you!
							Lawrence R. Amlord
							   Aug 15th, 2013
							   Fuzhou, China
Update my answer to Exercise 2.84.

Modified is the following file:

	Exercise_2.84.scm

Thank you!
							Lawrence R. Amlord
							   Aug 15th, 2013
							   Fuzhou, China