1. A fluid stream emerges from a chemical plant with a constant mass flow rate, w, and discharge into a river. It contains a waste material A at mass fraction wao, which is unstable and decomposes at a rate proportional to its concentration according to the expression ra=-ka PA (first-order reaction). To reduce pollution it is decided to allow the effluent stream to pass through a holding tank of volume V, before discharging into the river. The tank is equipped with an efficient stirrer that keeps the fluid in the tank very nearly uniform composition. At time t=0 the fluid begins to flow into the empty tank. No liquid flows out until the tank has been filled up to the volume V. Develop an expression for the concentration of the fluid in the tank as a function of time, both during the tank-filling process and after the tank has been completely filled. You should apply the macroscopic mass balance to the holding tank for species A (a) during the filling period and (b) after the tank has been filled. Volume flow rate Q-wla Concentration PA 7 River Well stirred tank with volume V