Senator BIRMINGHAM (South Australia) (14:42): My question is to the Minister representing the Minister for Climate Change and Energy Efficiency. I refer the minister to today's announcement by the Minister for Climate Change and Energy Efficiency of a new $12 million carbon tax advertising campaign, which is in addition to the existing $13.7 million public engagement campaign. How can the government have decided how much money— Honourable senators interjecting— The PRESIDENT: Order! As I have said, every senator is entitled to be heard in silence. If you disagree with anything that is being said you can debate it at the end of question time. Continue, Senator Birmingham. Senator BIRMINGHAM: How can the government have decided how much to spend on advertising its carbon tax when the government claims to still not know how much its carbon tax is going to be?