## 5 Discussion and Summary  
The verification of the models was carried out, and is still being carried out, by the main recipient and user of the proposed solutions, i.e., banks. Banks granting investment loans for construction projects are interested in the research results prepared by the author, and they implement them into everyday practice. The research results were presented and discussed with a leading bank in Poland during a seminar/training entitled \"Variability of the trend and size of deviations of the planned and incurred costs in various investment tasks\". The seminar was conducted for over 45 employees. The participants of the training were employees of, among others, the Real Estate Valuation and Analysis Office, the Risk Department, the Risk Management Division, and also the Investment Banking and Real Estate Financing Department. The training was a response to the needs of the financial market, which has a problem with unrealistic budget reserves being accepted by investors when granting investment loans. The correct financing of an investment depends on how the bank, but also the auditor--the Bank Investment Supervision--assesses the construction project. Banks try to adjust the budget of a construction project and take into account the actual cost by adopting differentiated budget reserves depending on construction groups/sectors and by reducing the budget failure rate from 0.8 (given by PMI) to a value corresponding with the adjusted budget reserve. The research results presented in this paper do not cover all the problems related to the modeling of construction projects. Within the scope of the discussed issue, the subject is developing and should be continued, e.g., by examining the possibility of using other methods, such as artificial intelligence methods, to predict cost curves and their areas in various construction projects. Moreover, it can be used to examine the relationship between the amounts of the performed construction works and the deviation of the actual cost from the budgeted one. It is also advisable to further update the knowledge base with new construction projects, because with an increasing number of analyzed construction projects, it will be possible to iteratively narrow the area of actual costs in various construction projects (shown in Figure 7). It will then be possible to provide banks with new, practical results in the form of, e.g., correction factors that will bring the budgeted cost closer to the actual cost. Figure 7: Iterative narrowing of the real cost area in various construction projects. The presented approach is the result of many years of research on the methodology and tools for modeling construction projects. As a result, a method was developed that allows the course of the actual implementation cost to be forecasted, the best fit of the cost curve to be determined, and the area of the correct cost planning for selected construction projects to be specified. The method was developed using a reliable knowledge base that contains archival information on various construction projects. The research extends the previously applied approach that uses the earned value method and aims to propose a comprehensive approach to forecasting cost curves. The developed model allows the decision-maker to receive an early warning about the possibility of the occurrence of cost overruns. By developing the original method, two previously used methods for controlling and monitoring construction projects were combined (the cumulative cost curve method--the \"S\" curve method and the earned value method) into one original course of cumulative cost curve (CCCC) method--the best fit of the cost curves and the area of the curves in selected construction projects. Monitoring that is carried out in accordance with the elaborated model that has specific parameters/\" an irregularity warning system\" allows for the effective cost management of a construction project and also reduces the possibility of cost overruns. Conceptualization, M.S. and J.K.; methodology, M.S.