$.$ The mean time to expose a single panel in a circuit$-$board plant is $2$ minutes with a standard deviation of $1\mathrm{.}5$ minutes. $($a$)$ What is the natural coefficient of variation? $($b$)$ If the times remain independent, what will be the mean and variance of a job of $60$ panels? What will be the coefficient of variation of the job of $60?($c$)$ Now suppose times to failure on the expose machine are exponentially distributed with a mean of $60$ hours and the repair time is also exponentially distributed with a mean of $2$ hours. What are the effective mean and CV of the process. The mean time to expose a single panel in a circuit$-$board plant is $2$ minutes with a standard deviation of $1\mathrm{.}5$ minutes. $($a$)$ What is the natural coefficient of variation? $($b$)$ If the times remain independent, what will be the mean and variance of a job of $60$ panels? What will be the coefficient of variation of the job of $60?($c$)$ Now suppose times to failure on the expose machine are exponentially distributed with a mean of $60$ hours and the repair time is also exponentially distributed with a mean of $2$ hours. What are the effective mean and CV of the process time for a job of $60$ panels? time for a job of $60$ panels?