## 4 Results
### Inventory Related Costs
#### 4.1.2 Transportation Costs  
On an individual SE level, minimal \(\mathrm{C_{T}}\) in a 7-day WS occurs for R = 15 and LT = 15 (R + LT = 30), with a value of 1623.85 EUR/year, while on the 5-day schedule, it occurs in  
Figure 5: (a) Increase in avg. \(\mathrm{C_{o}}\) for FR 99.9% per R + LT group for a 7-day compared to 5-day WS. (b) Relative change in avg. \(\mathrm{C_{o}}\) per R + LT group and WS for an FR 99.9% and SD 30 compared to FR 89.9%. R = 11 and LT = 15 (R + LT = 26), with a value of 1540.59 EUR/year. Maximal C\({}_{\rm T}\) occurs for R = 1 and LT = 0 (R + LT = 1) in an individual SE in a 7-day WS, with a 16990.75 EUR/year value. In a 5-day WS, maximal values are observed for identical operating conditions, with a 13162.73 EUR/year value. When analyzing average values of C\({}_{\rm T}\) per R and LT groups separately, maximal average C\({}_{\rm T}\) in a 7-day WS occurs for the R = 1, LT = 0 (R + LT = 1) group of SEs, with a value of 16840.52 EUR/year and minimal 1685.75 EUR/year for R = 15 and LT = 15 (R + LT = 30). Maximal average C\({}_{\rm T}\) in a 5-day WSs occur for the same group R = 1, LT = 0 (R + LT = 1) of SEs, with a value of 12877.39 EUR/year and minimal 1604.81 EUR/year for R = 15 and LT = 14 (R + LT = 29). Generally, with the increase in R + LT, average C\({}_{\rm T}\) decreases, as visible in Figure 6. When analyzing average values of C\({}_{\rm T}\) per R + LT groups, we can conclude that minimal average C\({}_{\rm T}\) occurs in R + LT = 30 and maximal for R + LT = 1 regardless of the WS and demand variability. For a 5-day WS, the minimal average C\({}_{\rm T}\) is approximately 1610.00 EUR/year, and the maximal is about 12880.00 EUR/year. For a 7-day WS, the minimal average C\({}_{\rm T}\) is approximately 1685.00 EUR/year, and the maximal is approximately 16840.00 EUR/year, regardless of demand variability. A reduction in average CT related to the increase in R + LT, i.e., slower deliveries and less frequent inventory reviews, is approximately eight times in a 5-day WS, whereas it is about ten times in a 7-day WS. Demand variability has an almost insignificant influence on average C\({}_{\rm T}\). On average, C\({}_{\rm T}\) is lower by 0.6% for SD 30 compared to SD 10 for a 5-day WS and 0.3% for a 7-day WS. The most considerable relative decrease in average C\({}_{\rm T}\), regardless of WS and demand variability, occurs for R + LT = 2/1 with an average reduction of 41% for a 5-day and 39% for a 7-day WS. With the increase in R + LT value for a single time unit, average C\({}_{\rm T}\) decreased 6.5% in a 5-day and 7.1% in a 7-day WS. Some groups with higher R + LT values show higher average C\({}_{\rm T}\) compared to lower R + LT groups. A maximal increase is noticed for a 7-day WS with a value of 3.2% regardless of demand variability. Figure 7a shows that the average CT for a 7-day WS is higher in all R + LT groups than for a 5-day WS. On average, the relative increase is 19.4%, regardless of demand variability. The relative difference in C\({}_{\rm T}\) between the 7-day and 5-day WSs shows no trends with the increase in R + LT. Maximum increases in average C\({}_{\rm T}\) are visible for R + LT = 2, with a 35.1% increase in the 7-day compared to 5-day WS, regardless of demand variability. Figure 6: (a) Average C\({}_{\rm T}\) per R + LT group for a 5-day WS and FR 99.9%. (b) Average C\({}_{\rm T}\) per R + LT group for a 7-day WS and an FR 99.9%. In the R + LT group, differences between the maximum and minimum C\({}_{\rm T}\) are above 41%, regardless of the WS and demand variability. The maximal difference in a 5-day WS is 86.3% for SD 30 and R + LT = 15. In a 7-day WS, the maximal difference occurs in R + LT = 11, with values of 71.6% for SD 30. Average C\({}_{\rm T}\) for an FR of 99.9% is higher in 95% of R + LT groups compared to an FR of 89.9% (114 of 120 scenarios), as visible in Figure 7(b) for high demand variability. In a 5-day WS, they are, on average, 4.9% higher compared to 8.1% in a 7-day WS, regardless of demand variability.