Write a chrome and firefox extension to configure/enable proxy connections

I need to have two extensions created, one for each browser type. The extensions will configure the proxy settings of the browser when running on both OSX and windows. The application will make a call to a server. A list of servers will be returned. The list of servers will be broken down into two different lists. The user should be able to select any server of either list and have the extension configure their browser to use that proxy server. A username and password will also need to be provided to the proxy server for authentication so that will need to be configured as well.