Measurements about the tensile strength of a metal fastener were obtained and the following results were obtained by working with a total of 30 subgroups, 6 observations in each sample. Calculate UCL, CL and LCL for the X-R control diagram. (Do not draw control diagrams.)

$\sum_{i=1}^{30}R_{i}=1350$

$\sum_{i=1}^{30}\bar{x_{i}}=12870$