4. A bottling company uses a filling machine to fill plastic bottles with a popular cola. The bottles are supposed to contain 300 milliliters (ml). In fact, the contents vary according to some normal distribution with mean u = 298 ml and standard deviation =3ml. a. What is the probability that the mean content of the bottles in a 36-pack is greater than 297.5ml? b. What is the probability that the mean content of the bottles in a 36-pack is between 297.5 ml and 298.5 ml?