I need all three questions answered please!

4. (Mean charts with known ) A quality inspector took five samples (k=5), each with four observations (n=4), of the length of time for glue to dry. The analyst computed the mean of each sample and then computed the grand mean. All values are in minutes. Use this information to obtain three-sigma (i.e., z=3 ) control limits for means of future times. It is known from previous experience that the standard deviation of the process is 0.02 minute. 5. (Mean charts with unknown ) Consider the same scenario in question 4 and now suppose that the quality inspector does not know standard deviation, , then obtain the control limits for means of future times. 6. (R-charts). Using the average range, R, found in question 5 , compute the control limits for a range chart