A driver is stuck in a traffic jam on the freeway. Nothing is moving. Suddenly a man knocks on the window. The driver rolls down his window and asks, "What's going on?" "Terrorists have kidnapped John Howard, Peter Costello, Kevin Rudd & Julia Gillard. They're asking for a $500 million ransom, otherwise they're going to douse them with petrol and set them on fire. We're going from car to car taking up a collection." The driver asks, "How much is everyone giving, on average?" "About a litre."