Seong-Un is a local fishery in Busan, the second mostpopulous city in South Korea. In 2017, an employee survey conducted by Seong-Un found that 55% of its employees were concerned about future health care benefits. A random sample of 90 of these employees were asked if they were now concerned about future health care benefits. Answer the following, assuming that there has been no change in the level of concern about health care benefits compared to the survey in 2017.
a. What is the standard error of the sample proportion who are concerned?
b. What is the probability that the sample proportion is less than 0.50?
c. What is the upper limit of the sample proportion such that only 3% of the time the sample proportion would exceed this value?