where, , , and are slack variables denoting input excess, output shortfall, and carry-over excess, respectively. This objective function is based on the input-oriented SBM model [59]. The main targets of evaluation of the objective function are excesses in both input resources and carry-over values. Since carry-over items have similar features as inputs, to be exact, a smaller amount is preferable to a larger amount, and both are accounted for in the objective function in a similar way