Add my answer to Exercise 2.21.

Included are the following 2 files:

	Exercise_2.21.pdf
	Exercise_2.21.tm

Thank you!
							Lawrence R. Amlord
							   May 28th, 2013
							   Xi'an, China
Add my answer to Exercise 2.22.

Included are the following 4 files:

	Exercise_2.22.pdf
	Exercise_2.22.scm
	Exercise_2.22.tm
	Test_for_Exercise_2.22.scm

Thank you!
							Lawrence R. Amlord
							   May 29th, 2013
							   Xi'an, China
Add my answer to Exercise 2.23.

Included are the following 4 files:

	Exercise_2.23.pdf
	Exercise_2.23.scm
	Exercise_2.23.tm
	Test_for_Exercise_2.23.scm

Thank you!
							Lawrence R. Amlord
							   May 29th, 2013
							   Xi'an, China