A coal-burning power plant tests and measures three specimens of coal each day to monitor the percentage

Question:

A coal-burning power plant tests and measures three specimens of coal each day to monitor the percentage of ash in the coal. The overall mean of 30 daily sample means and the combined standard deviation of all the data were and s = .07, respectively. Construct an chart for the process and explain how it can be of value to the manager of the power plant.