Using a 3D printer the mean time to produce a part is 5 hours (4 hours printing and 1 hour post-processing) with a standard deviation of 30 mins.

a) If the times are independent, what will be the mean and variance of processing times for a job of 50 parts?

b) What is the coefficient of variation (CV)? Suppose the times to failure of the EOS machine are exponentially distributed with a mean of 80 hours, and repair times are also exponentially distributed with a mean of 1 hour.

c) What is the effective CV of the process for a job of 50 parts?