Inspectors Want to Develop Process Control Charts to Measure the Weight

Inspectors want to develop process control charts to measure the weight of crates of wood. Data (in pounds)from three samples are:
Sample Crate 1 Crate 2 Crate 3 Crate 4
1 18 38 22 26
2 26 30 28 20
3 26 26 26 26
(a)What is the upper control limit for the R chart?
(b)What is the lower control limit for the R chart?
(c)What is the upper control limit for the x-bar chart?
(d)What is the lower control limit for the x-bar chart?
(e)Is the process in a state of control? If not, why not?