Xamarin Native and Forms Development

I am looking for an experienced, preferably senior developer with demonstrable experience in [login to view URL] to help me build a cross platform mobile application. Individuals and development firms may respond, quoting your default hourly rate as transparently as possible. You should be prepared to explain and demonstrate at least one pre-existing Xamarin app in Android and iOS, referencing code as necessary. This app must have, at a minimum, (a) user authentication to Facebook/Google and (b) calls to REST API's. In order to save time in the evaluation process, if you could share at least a few portfolio apps or Web sites in the initial email response, that would be helpful.