A pulp consisting of only quartz and water is fed quiescently into the classifier at 30% solids by weight. If a particle settles through Zone A and into Zone B, the particle will not overflow the classifier but will report to the sands. The depth of Zone A is 2 inches. It is desired that particles finer than 100 microns report to the overflow, and particles courser than 100 microns report in the classifier sands. The feed rate of dry solids is 20 tons/hour. What is the retention time (in seconds) for a 100 micron particle that reports to the overflow? What is the settling pool cross sectional area (in ft2) of the classifier? Assume the pulp in Zone A contains 30% solids by weight.