For the 71 trading days from January 3, 2017, to April 18, 2017, the daily closing price of IBM stock (in $) is well modeled by a Normal model with mean $174.853 and standard deviation $4.508. According to this model, and using the 68-95-99.7 Rule to approximate the probabilities rather than using technology to find the values more precisely, what is the probability that on a randomly selected day in this period the stock price closed a) above $179.36? b) below $183.87? c) between $161.33 and $188.38? d) Which would be more unusual, a day on which the stock price closed above $187 or below $168