Response to the following questions:
1. Briefly summarize the accounting for an investment in debt securities held to maturity.
2. Briefly describe how to determine and record any subsequent increases or decreases in the fair value of an investment in available-for-sale securities.
3. Briefly describe how to determine and record the gain or loss on the sale of an investment in available-for-sale securities.
If possible, please give examples to better understand your response.