A supplier to the aerospace industry specializes in a steel heat treatment process. The process can take batches of up to $60$ parts, and takes an average of $2$ hours to process a batch, regardless of the number of parts in the batch, with a standard deviation of $0\mathrm{.}5$ hours. The parts arrive to the heat treatment process one at a time according to a Poisson stream $($i$.$e$.,$ exponential interarrival times$)$ at a rate of $20$parts$/$hr$.$