the courier service company has found that their time of parcels to client is normally distributed with a mean of 45 minutes and a standard deviation of 8 minutes. the probability that a randomly selected parcel will take less than 48 minutes to deliver is

Answer 1

A handy tool for Z table problems is at

http://davidmlane.com/hyperstat/z_table.html

Play around with a bit, and get comfortable with this kind of question.