At a Fast-Food Restaurant,if the Average Time to Serve a Customer

Multiple Choice

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

A) UCL = 4.04,LCL = 3.46
B) UCL = 5.08,LCL = 4.94
C) UCL = 5.75,LCL = 1.75
D) UCL = 3.91,LCL = 3.60