On April 10, 2015, the Company entered into an exchange agreement whereby the Company received an investment in an account receivable with annual installment payments of $117,000 for 11 years, through 2026, totaling $1,287,000 in exchange for 757,059 shares of Mentor Common Stock obtained through exercise of 757,059 Series D warrants at $1.60 per share plus a $0.10 per warrant redemption price.

The Company valued the transaction based on the market value of Company common shares exchanged in the transaction, resulting in a 17.87% discount from the face value of the account receivable. The discount is being amortized monthly to interest over the 11-year term of the agreement. The investment in account receivable is supported by an exchange agreement and consisted of the following:

For the three months ended June 30, 2020 and 2019, $19,872 and $19,999 of discount amortization is included in interest income, respectively. For the six months ended June 30, 2020 and 2019, $38,217 and $39,997 of discount amortization is included in interest income, respectively.