There are 150 American students, 75 Chinese students and 50 Japanese students in a school. (a) If a student representative is to be chosen from the school, how many different choices are there? [1 mark] (b) If two students are to be chosen, one must be an American and the other must be a Chinese, how many different choices are there? [2 mark] (c) If two students are to be chosen and the case of having one American and one Chinese is not allowed, how many different choices are there?