Read this and answer the question. If the question is unanswerable, say "unanswerable".

Ship transport is an important component of Melbourne's transport system. The Port of Melbourne is Australia's largest container and general cargo port and also its busiest. The port handled two million shipping containers in a 12-month period during 2007, making it one of the top five ports in the Southern Hemisphere. Station Pier on Port Phillip Bay is the main passenger ship terminal with cruise ships and the Spirit of Tasmania ferries which cross Bass Strait to Tasmania docking there. Ferries and water taxis run from berths along the Yarra River as far upstream as South Yarra and across Port Phillip Bay.

Which is Australia's busiest port?
The Port of Melbourne