add two auxiliary subproblem in Problem 6-2.

Modified is the following file:

	6-2.tm

Thank you!
							Lawrence X. Amlord
							  Jul 3rd, 2014
							  Xi'an, China
add solution to Part c in Problem 6-2.

Modified is the following file:

	6-2.tm

Thank you!
							Lawrence X. Amlord
							  Jul 5th, 2014
							  Xi'an, China
complete solution to Part c of Problem 6-2.

Modified is the following file:

	6-2.tm

Thank you!
							Lawrence X. Amlord
							  Jul 5th, 2014
							  Xi'an, China
add solution to Part c in Problem 6-2.

Modified is the following file:

	6-2.tm

Thank you!
							Lawrence X. Amlord
							  Jul 6th, 2014
							  Xi'an, China