please help me solve this

2. [8 marks = 3+2+3] For one type of surgery, patient recovery times are normally distributed with a mean of 5.9 days and a standard deviation of 1.8 days. (Rounded to FOUR decimal places) (a) What is the probability that a randomly chosen patient takes between 4 and 7 days to recover? (b) Find the value of the 80th percentile of the recovery times. (Show the percentile on a graph and shade the corresponding area) (c) What is the probability that in a random sample of 50 patients, the mean recovery time is longer than 8 days