In redesigning jet ejection seats to better accommodate women as pilots, it is found that women's weights are normally distributed with mean 60 kg and standard deviation 8 kg.

a) If a woman is randomly selected, find the probability that she weighs more than 55 kg.

b) Find the weight separating the bottom 10% and from the top 90%.

c) Find the maximum and minimum weights which include in the middle 30% of the women weights.

d) If a sample of 20 women is selected, find the probability that the mean of the sample will be less than 63 kg.