add solution to Exercise 5.11.

Included are the following 2 files:

	Exercise_5.11.pdf
	Exercise_5.11.tm

Thank you!
							Lawrence X. A. Yan
							  Aug 27th, 2014
							  Fuzhou, China
add solution to Exercise 5.12.

Warning: This solution still contains a few glitches and need to be further
         debugged.

Included are the following 3 files:

	Exercise_5.12.scm
	Exercise_5.12.tm
	ch5-regsim-var-ex_5.12.scm

Thank you!
							Lawrence X. A. Yan
							  Aug 30th, 2014
							   Xi'an, China