The next step is to carry out a thorough sensitivity analysis of the results of the previous stage. This was done using SIMLAB V2.2 program (SIMLAB, 2004) developed by the Joint Research Centre of the European Commission, which uses the Monte Carlo method to determine the uncertainty level of the model predictions and input variables, with the aim of identifying the effect of factor and weight variations on the model results. This ensures the results are more reliable and identifies the factors by which they are significantly influenced (Gómez and Barredo, 2005; Saltelli et al., 2000).