When calculating a Cp$,$ how is the process sigma determined?Group of answer choicesEstimate what standard deviation would validate all samples as acceptable, and use that.Divide the average of the first five samples by $6($for six sigma performance$)$Use the sigma calculated from the square root of the variance of the customer specifications.If there is not enough historical data to calculate the actual process sigma, it can be estimated by the sample standard deviation using constants, for the example of variable charts, you would calculate it by using the equation where sigma equals Rbar divided by d$2.$