The courier company guarantees pick up of packages within $11$ minutes of the scheduled time. Therefore, there are two requirements: on time and up to $11$ minutes late. The information for the examples taken is as follows: n $=4,$ X double bar $=13\mathrm{.}00,$ R bar $=4\mathrm{.}9.$ Assume normal distribution and process in control. Determine Capability index Cp$.$