1. A computer-implemented method for determining an offer set, comprising: accessing, using one or more data processors, a global set of action items, wherein the global set includes assignable marketing action items, and wherein action items are assignable to a plurality of customers; generating, using the one or more data processors, initial offer sets for each customer using an objective function and one or more individual constraints, wherein an initial offer set includes one or more action items, and wherein an individual constraint limits assignable action items for a customer; adjusting, using the one or more data processors, the objective function using one or more aggregate constraints and a Lagrange relaxation technique, wherein an aggregate constraint limits assignable action items for a plurality of customers; calculating, using the one or more data processors, initial quality values for the initial offer sets using the adjusted objective function and a subgradient algorithm; generating, using the one or more data processors, revised offer sets for each customer using the adjusted objective function; calculating, using the one or more data processors, revised quality values for the revised offer sets using the adjusted objective function and the subgradient algorithm; and determining, using the one or more data processors, an offer set for each customer using the initial quality values and the revised quality values, wherein each offer set is selected from the initial offer sets or from the revised offer sets.