TYCO Inc. purchased several investments in debt securities during 2018, its first year of operations. The following information pertains to these securities. The fluctuations in their fair values are not considered permanent.

Held to Maturity Securities:	Fair Value 12/31/2017			Fair Value 12/31/2018			Amortized Cost 12/31/2017			Amortized Cost 12/31/2018
ABC Co. Bonds	$	375,000		$	400,000		$	367,500		$	360,000
Trading Securities:	Fair Value 12/31/2017			Fair Value 12/31/2018			Cost
DEF Co. Bonds	$	48,000		$	59,500		$	66,000
GEH Inc. Bonds	$	47,000		$	77,000		$	39,000
IJK Inc. Bonds	$	44,000		$	38,500		$	32,900
Available for Sale Securities:	Fair Value 12/31/2017			Fair Value 12/31/2018			Cost
LMN Co. Bonds	$	130,500		$	150,400		$	140,000

What balance sheet amount would TYCO report for the total of its investments in debt securities at 12/31/2017?

A) $637,000.

B) $644,500.

C) $645,400.

D) None of these answer choices are correct.

Note: Can you show me step-by-step why the correct answer is A. $637,000? Please show your calculations and explanations on Word or Excel as handwriting can be difficult to read. I appreciate it.