## 4 Results
### Inventory Related Costs  
#### 4.1.1 Ordering Costs  
Minimal C\({}_{\text{o}}\) on a level of individual SE in a 7-day WS occurs for R = 15 and LT = 15, with a value of 220.00 EUR/year; the same values as in a 5-day WS, but in it, values of C\({}_{\text{o}}\) occur in 10 different groups (from R + LT = 24 to R + LT = 30). Maximal C\({}_{\text{o}}\) on an individual SE occurs for R = 1 and LT = 0, with a value of 7300.00 EUR/year in a 7-day and 5220.00 EUR/year in a 5-day WS. When analyzing average values of C\({}_{\text{o}}\) per R and LT groups separately, maximal average C\({}_{\text{o}}\) in a 7-day WS occurs for the R = 1, LT = 0 (R + LT = 1) group of SEs, with a value of 7219.30 EUR/year and minimal 239.40 EUR/year for R = 15 and LT = 15 (R + LT = 30). Maximal average C\({}_{\text{o}}\) in a 5-day WS occurs for the same group R = 1, LT = 0 (R + LT = 1) of SEs with a value of 5067.20 EUR/year and minimal 239.40 EUR/year for R = 15 and LT = 11 and 12. Generally, with the decrease in R + LT, average C\({}_{\text{o}}\) decreases, as visible in Figure 4. When analyzing average values of C\({}_{\text{o}}\) per R + LT groups, minimal average C\({}_{\text{o}}\) occurs in R + LT = 30 and maximal for R + LT = 1 regardless of the WS and demand variability. Minimal average C\({}_{\text{o}}\) in both WSs is almost identical. For a 5-day WS, the minimal average C\({}_{\text{o}}\), regardless of demand variability, is about 239.50 EUR/year. The maximal average C\({}_{\text{o}}\) in the same WSs occurs for R + LT = 1, with values of 5204.20 EUR/year for SD 10 and 4930.20 EUR/year for SD 30. For a 7-day WS, the minimal average C\({}_{\text{o}}\), regardless of demand variability, is about 239.40 EUR/year. The maximal average C\({}_{\text{o}}\) in the same WSs occurs for R + LT = 1, with values of 5204.20 EUR/year for SD 10 and 4930.20 EUR/year for SD 30. For a 7-day WS, the minimal average C\({}_{\text{o}}\), regardless of demand variability, is about 239.  
mal average \(\mathrm{C_{o}}\) in the same WSs is noticed for R + LT = 1, with values of 7295.00 EUR/year for SD 10 and 7143.60 EUR/year for SD 30. Demand variability has a meager influence on average \(\mathrm{C_{o}}\). On average, \(\mathrm{C_{o}}\) are lower by 0.9% for SD 30 compared to SD 10 for a 5-day WS and 0.4% in a 7-day WS. On both WSs, the highest relative reduction in average \(\mathrm{C_{o}}\) due to higher demand variability is noticed in R + LT = 1, with a value of 5.3% for a 5-day and 2.1% for a 7-day. The impact of R + LT changing from minimal to maximal values on average \(\mathrm{C_{o}}\) is from about 21 times in a 5-day WS. In contrast, it is about 30 times for a 7-day WS, depending on demand variability. Regardless of the WS, the most significant relative decrease in average \(\mathrm{C_{o}}\) occurs for R + LT = 2/1, with a reduction of about 50%, irrespective of demand variability. On average, with the increase in R + LT value for a single time unit, average \(\mathrm{C_{o}}\) decreases about 9% in a 5-day WS while on a 7-day WS, about 10% regardless of demand variability. Some groups with higher R + LT values show higher average \(\mathrm{C_{o}}\) compared to the R + LT groups with lower values. On a 5-day WS and for low demand variability, there are two occurrences with an average increase of 1.4%, while for high demand variability, there are three occurrences with a 1.0% increase. On a 7-day WS, SD 10 and SD 30 experienced six occurrences, with increases of 3.1% and 3.2%, respectively. As visible in Figure 5a, the average \(\mathrm{C_{o}}\) for a 7-day WS compared to a 5-day WS is higher. On average, regardless of demand variability, the relative increase is 31%. Maximum increases are noticed for the R + LT = 25 group, where for SD 10, they are 51.7%, and for SD 30, 55.9% on average. Average \(\mathrm{C_{o}}\) is slightly higher for an FR of 99.9% compared to an FR of 89.9%, as visible in Figure 5b for high demand variability.