A Qantas airplane has 250 passengers on board. Of these 250, 100 are Australian, 75 are Asian, 50 European and 25 American. They are seated completely randomly in the plane. As a general measure of safety, before departure, the police checks the carry-on luggage of a number of passengers that are chosen at random. Calculate the probability that: The first four randomly picked passengers are from four different continents. The first four randomly picked passengers are all Asian. The first three randomly picked passengers are from three different continents. Of the first four passengers, two are Australian, and two are European.