A supplement to the EPQ with partial backordering and phase-dependent backordering rate

In this note, we extend Pentico et al. (2011)'s [1] EPQ model where the authors considered two different backordering rates during shortage period; they assumed the backordering rate increases only from the start of production phase. We propose two models that allow the backordering rate to increase anytime during the production phase, and thus provide more flexibility for decision-makers to vary the backordering rate.