11. A work sampling study is to be conducted to determine the idleness of the milling machines in the mill- ing section of the large engineering world. In a preliminary study, 100 observations were made and 25 observations showed the machine to be idle. What will be the number of random observations required to be made to obtain a confidence level of 95% and an accuracy of 5% ? If after 600 observations, it was found that the incidents of machines being idle are 30%, what would be the revised number of random observations to be made?