A process that is in control has a mean of = 12.5 and a standard deviation

Question:

A process that is in control has a mean of μ = 12.5 and a standard deviation of σ = .8.
a. Construct the x-bar control chart for this process if samples of size 4 are to be used.
b. Repeat part (a) for samples of size 8 and 16.
c. What happens to the limits of the control chart as the sample size is increased? Discuss why this is reasonable.