A cutting tool wears out with a time to failure that is normally distributed with a mean of 10 working days and a standard deviation of 2.5 days.
a) Determine its design life for a reliability of 0.99
b) Find the reliability if the tool is replaced every,(i) day (ii) two days (iii) five days
c), Determine the probability that the cutting tool will last one more day given it has been in use for 5 days.