derivation in XML Schema

I was unable to determine the answers to these questions by reading the 'Structures' part of XML Schema, http://www.w3.org/TR/xmlschema-1

1. Given types B, E, and R where E is an extension of B, and R is a restriction of E, is R a restriction or extension of B, or neither?

2. Similarly, given B, E, and R where R is a restriction of B and E is an extension of R, is E a restriction or extension of B or neither?

3. For the most derived type in each chain (R in the first and E in the second), when is it allowed and when prohibited by {prohibited substitutions} on B?

4. For the most derived type in each chain (R in the first and E in the second), when is it allowed and when prohibited by {disallowed substitutions} on some element declared to have type B?  That is, with what values of {disallowed substitions} will such an element validate with an xsi:type of R and E respectively, and with what values will it not validate?

[If you respond, please include my email address in the list of recipients as I have not yet figured out how to subscribe to this list (the references on the schema activity pages at W3 point only to the archives).  Thank you.]

Jeff