correct an error statement in solution to Exercise 11.2-3.

Modified are the following 2 files:

	11.2-3.pdf
	11.2-3.tm

Thank you!
							Lawrence X. Amlord
							  May 12th, 2014
							  Xi'an, China
add solution to Exercise 11.2-4.

Included are the following 2 files:

	11.2-4.pdf
	11.2-4.tm

Thank you!
							Lawrence X. Amlord
							  May 12th, 2014
							  Xi'an, China