Can someone explain how to get to this solution please

The IRS is concerned with improving the accuracy of tax information given by its representatives over the telephone. Previous studies involved asking a set of 25 questions of a large number of IRS telephone representatives to determine the proportion of correct responses. Historically, the average proportion of correct responses has been 70 percent. Recently, IRS representatives have been receiving more training. On April 26, the set of 25 tax questions were again asked of 20 randomly selected IRS telephone representatives. The proportions of correct answers were: 16,21,19,16,15,16,21,13,17,13,24,16,22,15,19,15,23,17,21,and14. a. What are the upper and lower control limits for the appropriate p-chart for the IRS? Use z=3. The UCL Cp equals and the LCLp equals (Enter your responses rounded to four decimal places. If your answer for LCLp is negative, enter this value as 0.) b. Is the tax information process in statistical control? Since there are no data points outside of the control limits statistical control. the process is considered to be