The upper and lower class limits for the c-chart are given by the formula:

`UCL_c=barc+3sqrtbarc`

`LCL_c=barc-3sqrtbarc`

`barc` = Number of defects/Observations

`barc=266/50=5.32`

`UCL_c=5.32+3sqrt5.32`

`UCL_c=12.23953756`

`UCL_c~~12.24`

`LCL_c=5.32-3sqrt5.32`

`LCL_c=5.32-6.919537557=-1.599537557`

`:.LCL_c=0`