Add my answer to Exercise 2.67.

Included are the following 2 files:

	Exercise_2.67.scm
	Test_of_Exercise_2.67.scm

Thank you!
							Lawrence R. Amlord
							   Jul 24th, 2013
							   Xi'an, China
Add my answer to Exercise 2.68.

Included are the following 2 files:

	Exercise_2.68.scm
	Test_of_Exercise_2.68.scm

Thank you!
							Lawrence R. Amlord
							   Jul 24th, 2013
							   Xi'an, China