Add the third session code in section 3.5.3.

Modified is the following file:

	3.5.3_Exploiting_the_Stream_Paradigm.scm

Thank you!
							Lawrence X. Amlord
							  Dec 5th, 2013
							  Xi'an, China
Add my answer to Exercise 3.73.

Included are the following 2 files:

	Exercise_3.73.scm
	Test_for_Exercise_3.73.scm

Thank you!
							Lawrence X. Amlord
							  Dec 5th, 2013
							  Xi'an, China
Add my answer to Exercise 3.74.

Included is the following file:

	Exercise_3.74.scm

Thank you!
							Lawrence X. Amlord
							  Dec 5th, 2013
							  Xi'an, China