Add my answer to Exercise 2.56.

Included are the following 2 files:

	Exercise_2.56.scm
	Test_for_Exercise_2.56.scm

Thank you!
							Lawrence R. Amlord
							   Jul 18th, 2013
							   Xi'an, China
Add my answer to Exercise 2.57.

Included are the following 2 files:

	Exercise_2.57.scm
	Test_for_Exercise_2.57.scm

Thank you!
							Lawrence R. Amlord
							   Jul 18th, 2013
							   Xi'an, China
Add my answer to Exercise 2.58.

Included are the following 2 files:

	Exercise_2.58.scm
	Test_for_Exercise_2.58.scm

Thank you!
							Lawrence R. Amlord
							   Jul 18th, 2013
							   Xi'an, China