Can you explain what a mixed shelf is? For example, Raytheon announced a $3 billion mixed shelf.

A “mixed shelf” has to do with the registration of securities with the SEC. When a company does a “shelf registration,” they are registering securities to issue at some future, undetermined date as needed from time to time, saving them from having to update the registration statements every time there is an issuance of securities covered by the registration. A “mixed shelf” is the shelf registration of different types of securities, such as a mixture of debt and equity. One could do a mixed shelf of common stock, preferred stock, and convertible debt securities, up to an amount specified in the registration.