$2.$ A process control chart shows the process average $($mean$)$ of $6\mathrm{.}5$ days from order receipt to order fulfillment with an average range of $1\mathrm{.}6$ days. The sample size is $4$ orders. What is the upper control limit $($UCL$)$ days and the lower control limit $($LCL$)$ days for the process? Show your calculation and highlight your answer below.