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[20 marks] It is known that 20% of all calls coming into a telephone exchange are long distance calls. During a certain period of time, 15 calls came into the exchange. What is the probability that at least three are longdistance calls? [20 marks] In the old days, there was a probability 0.8 of success in an}r attempt to make a telephone call. Suppose 1800 calls came into the exchange. Use normal approximation of the binomial to calculate the probability that the number of longdistance calls are between 700 and 750? [20 marks] Using least square method, nd the line of best t for the following set of 9 data points: (90, 94), (67, 75), (50, 54), (89, 90), (30, 60), (75, 82), (80, 90), (70, 85), (83,88)