This Demonstration shows a calculation of the monetary profit for running a continuous stirred-tank reactor (CSTR) or a plug-flow reactor (PFR), as a function of reactor volume. Model either a first-order or an autocatalytic reaction and set the feed concentrations of reactant and product with sliders. Use sliders to set the value of the product and the costs of the reactant and reactor. Display plots for profit or for reactant and product concentrations versus reactor volume. Click and drag the black dot on the profit versus reactor volume plot; profit and conversion at the selected volume are displayed below. Check "optimize" to solve for the reactor volume with the highest profit. The cost of separations is assumed to be negligible and unreacted reactant is recycled back into the feed.