6. (b) The letters of the word CALCULUS are arranged in a row. How many different arrangements are possible? If one arrangement is chosen at random, what is the probability that it begins with “U” and ends with “U”? 6. (c) The seven characters (three letters and four numerals) in ABC2003 are arranged in a row. How many different arrangements are possible? If one arrangement is chosen at random, what is the probability that the three letters will be together?