At a fast-food restaurant, if the average time to serve a customer is 3.75 minutes for 10 samples of size 5 , and the average range for the samples is 0.50 minutes, the upper and lower control limits for a 3 -sigma x-chart are UCLUCLUCLUCL=3.91,LCL=3.60=5.75,LCL=1.75=4.04,LCL=3.46=5.08,LCL=4.94