7.   Investments in Debt and Equity Securities

Debt Securities

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Investments in debt securities consist of AA and A rated corporate bonds bearing interest at rates from 0.25% to 3.5% with maturities from April 2022 to February 2024. The components of investments in debt securities are as follows (in thousands):

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The fair value of available-for-sale debt securities, by contractual maturity, was as follows (in thousands):

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Amortization of premiums paid on the debt securities amounted to $74,000 and $80,000 for the three months ended March 31, 2022 and 2021, respectively. Amortization of premiums paid on the debt securities amounted to $269,000 and $130,000 for the nine months ended March 31, 2022 and 2021, respectively.

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Equity Security – at cost

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As discussed above, the Company acquired Series A-2 Preferred shares of RubrYc valued at $1,760,000.  The Company classified the investment as noncurrent as it is management's intent not to sell the investment in the near term.