Could you explain me this question, please?

Problem 10-25 (Algo) Resistors for electronic circults are manufactured on a high-speed automated machine. The machine is set up to produce a large run of resistors of 1,000 ohms each. Use Exhibit 10.13. To set up the machine and to create a control chart to be used throughout the run, 15 samples were taken with four resistors in each sample. The complete list of samples and their measured values are as follows: Use three-sigma control limits. SAMPLE NUMBER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 READINGS (IN OHMS) 1995 1999 1015 978 1030 1015 979 1030 1994 1030 1009 993 960 1017 991 1927 1019 1010 1008 988 999 978 972 994 979 1021 1010 989 980 1028 973 1019 977 978 978 1893 985 985 985 994 988 1939 1012 981 980 1012 1012 998 1084 1002 971 1013 1013 993 1011 981 1030 991 991 1030 a. Calculate the mean and range for the above samples. (Round "Mean" to 2 decimal places and "Range" to the nearest whole number.) Mean Range Sample Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 b. Determine X and R. (Round your answers to 3 decimal places.) X bar R bar c. Determine the UCL and LCL for a X chart (Round your answers to 3 decimal places.) UCL LCL d. Determine the UCL and LCL for R-chart. (Leave no cells blank - be certain to enter "0" wherever required. Round your answers to 3 decimal places.) UCL LCL