Estimate the Process Standard Deviation

Estimate the process standard deviation.
-An automatic filling process is used to dispense hand sanitizer into small purse size
Bottles. The target weight is 75 ml. The company has initiated control charting to
Stabilize and improve the automatic filling process. For each of twenty-five samples
Consisting of four bottles, the contents were measured and the mean weight and range
Were determined. The average of the means across all samples was found to be 72.5 ml.
And the average range was 2.75 ml. The estimate of the process standard deviation is

A) 2.75 ml
B) 2.44 ml
C) 1.88 ml
D) 1.34 ml
E) None of the above