The enzyme monoamine oxidase catalyzes the oxidation of amines to aldehydes. For tryptamine, Km for the enzyme is 4.0 x 10-4 M, and vmax = k2[E]0 = 1.6 x 10-3 mM/min at pH 8. Find the concentration of a solution of tryptamine that reacts at a rate of 0.18 mM/min in the presence of monoamine oxidase under the above conditions. Assume that [tryptamine] ,, Km.