It is found that the standard deviation of the diameters of rivets produced by a certain machine over a long period is 0.018 cm. The diameters of a random sample of 100 rivets produced by this machine in a day have a mean value of 0.476 cm. If the machine produces 2500 rivets per day, solve the given engineering problem under following conditions i) ii) The 90% confidence limits The 97% confidence limits for an estimate of the mean diameter of all the rivets produced by the machine in a day.