A tote box of parts arrives at an inspection station. The inspector selects a random number of parts for inspection; they are inspected individually. The tote boxes arrive at a Poisson rate of 2 per minute. The number of parts selected for inspection is equally likely to be 1, 2, 3, or 4. The inspection time per part is exponentially distributed with a mean of 6 seconds. On average, how many seconds will parts be waiting to be inspected? Recall, Var (X)  E(X2)  [E(X)]2.