why is there a market for bonds?

Answer in 3-4 paragraphs. APA format with in-text references.

In chapter 6, we explored how to value bonds. If all investors are using this method, why does the same bond buy or sell at different prices? In other words, why is there a market for bonds? Why do some financial analysts treat preferred stock as a special type of bond, rather than as an equity security? Include in your discussion the relationship between bond prices and interest rates.