Pursuant to N.C. Gen. Stat. § 105-264, “[i]t is the duty of the Secretary to interpret all laws administered by the Secretary. An interpretation by the Secretary is prima facie correct.” Pursuant to N.C. Gen. Stat. § 105-264.2, “[a] written determination applies the tax law to a specific set of existing facts furnished by a particular taxpayer. A written determination is applicable only to the individual taxpayer addressed and as such has no precedential value except to the taxpayer to whom the determination is issued. A written determination includes a private letter ruling.