Using the sample of observation in this excel sheet, calculate the following quality & performance metrics for the process under observation. Note that the customer specifies the two bounds as $75$ and $90.$ Answer $4$ questions below using excel sheet.

$1.$ The upper control limit for X$-$bar Control Chart is $\_\_\_\_\_\_.$ Please enter the numerical value below $($rounded to two places of decimal, if any$).$

$2.$ The lower control limit for R Control Chart is $\_\_\_\_\_\_\_\_.$ Please enter the numerical value below $($rounded to two places of decimal, if any$).$

$3.$ The process capability ratio is $\_\_\_\_\_\_\_\_\_.$ Please enter the numeric value below $($rounded to two places of decimal, if any$).$

$4.$ The process capability index is $\_\_\_\_\_\_\_\_\_\_\_\_.$ Please enter the numeric value below $($rounded to two places of decimal, if any$).$