In this paper, we consider a deterministic economic order quantity model with generalized type demand,
deterioration and unit purchase cost functions under two levels of trade credit policy. Our objective is
to find the optimal values of selling prices, replenishment number and replenishment scheme which
maximize the total profit over the finite planning horizon. We establish the inventory system and provide
structural properties of the optimal solution that facilitate computation. A particle swarm optimization
with constriction factor is coded and used to solve the mixed-integer nonlinear programming problem
by employing the properties derived from this paper. At the end, some numerical examples are used to
illustrate the features of the proposed model.