12. A repair garage can order a particular component overnight for delivery at the start of the working day. The demand for this component is normally distributed with a mean of 50 components/day and a standard deviation of 15 components/day. How many of these components should the garage hold at the beginning of the day, in order that there is a probability of 99% that all requests are satisfied within the day?11. The marks of 500 candidates in an examination are normally distributed with a mean of 45 marks and a standard deviation of 20 marks. What is the interquartile range of the distribution