Update my answer to Exercise 2.73.

Included are the following 2 files:

	Exercise_2.73.pdf
	Exercise_2.73.tm

Thank you!
							Lawrence X. Amlord
							  Dec 15th, 2013
							  Xi'an, China
Add my answer to Exercise 4.3.

Included is the following file:

	Exercise_4.3.scm

Thank you!
							Lawrence X. Amlord
							  Dec 15th, 2013
							  Xi'an, China