9. Long-Term Debt

As of December 31, 2016, the total principal balance and estimated fair value of our long-term debt was $3.0 million. As of March 31, 2017, the total carrying value and estimated fair value of our long-term debt was $4.0 million. These estimated fair values are based on Level 3 inputs. Interest rate of the Note approximates market interest rates. As of March 31, 2017 and December 31, 2016, the unamortized discount on the Note was $62,398 and $155,996, respectively.

Scheduled principal payments, including accrued interest through May 31, 2017 to be included in principal, are as follows:

2017	$	––
2018		531,250
2019		1,062,500
2020		1,062,500
2021		1,062,500
Thereafter		531,250
Total	$	4,250,000