add solution to Exercise 4.65.

Included are the following 2 files:

	Exercise_4.65.pdf
	Exercise_4.65.tm
	Exercise_4.65.scm

Thank you!
							Lawrence X. Amlord
							  Jul 22nd, 2014
							  Xi'an, China
add solution to Exercise 4.66.

Included are the following 2 files:

	Exercise_4.66.pdf
	Exercise_4.66.tm

Thank you!
							Lawrence X. Amlord
							  Jul 23rd, 2014
							  Xi'an, China
add solution to Exercise 4.68.

Included is the following file:

	Exercise_4.68.scm

Thank you!
							Lawrence X. Amlord
							  Jul 23rd, 2014
							  Xi'an, China