12. It is estimated that the time that a well-known rock band, the Living Ingrates, spends on stage at its concerts follows a normal distribution with a mean of 200 minutes and a standard deviation of 20 minutes. What proportion of concerts played by this band lasts between 180 and 200 minutes? 13. The amount of time necessary for a student of statistics to solve assignments is, on average, 15 minutes. This can be modeled as a random normal variable with a standard deviation of 2 minutes. Calculate the probability that an assignment is instead solved between 14 and 18 minutes