Introduction

Money laundering is the incorporation of money acquired through illegal transactions in the grey economy into normal financial and economic flows, which implies the granting of legal illegally acquired cash which - first by transferring to a bank account, is transferred into giro money and then from there to cash(Miletić et al., 2021). At the same time, money laundering also involves injecting money into the normal economic flows which came from criminal activity (drug and arms trafficking, smuggling, robbery, organized crime, tax avoidance, corruption, etc.) to prevent detection of its origin(Milojević et al., 2018).

The gray economy in the country leads to an increasing criminalization of society: at the beginning it creates the impression that the country is prospering, but soon the gray economy operators and money launderers gain reputation, richness and power and they are trying to take control of the entire financial and economic system.(Krstić, & Vukasović, 2018; Milosavljević Pantelejić Đ., Međedović, 2019) Such countries have no problem with crime because they cannot control it, since criminal organizations control the state. Therefore, anti-money laundering measures, which will prevent criminals from using or restrict their illicit acquisition of property, are crucial in the state's fight against organized crime(Avakumović et al., 2021).

The problem observed in this paper is the selection of an appropriate strategy to reduce the risk of money laundering and the gray economy through banks and to include more concepts that need to be defined initially.(Simić, Teuta, Yang, 2019) Choosing the best banking strategy is the aim of this problem. Based on the definition of decision-making that it is the choice of one of a set of possible alternatives(Arce et al., 2015; Falagario et al., 2012), where there must be at least two alternatives in the set, it can be concluded that the application of decision-making theory in the procedure itself is possible.

The definition of the criterion plays an important role in the decision-making process. The term "creature" refers to attributes that are related to the alternatives between which we make the selection. They can be divided into qualitative and quantitative criteria depending on the degree of measurability.(Mihajlović et al., 2016). Quantitative criteria are those that can be accurately measured and expressed by different units of measurement. Qualitative criteria are those that cannot be expressed numerically(Veslinović, 2014). They can be classified into two sub- groups: attributes whose values cannot be accurately measured, but can still be classified by “intensity” and attributes by which no quantitative comparison of alternatives can be made.

Formulating the mathematical model of multicriteria decision making

The stability of the obtained solution in case of change of criteria can be performed by the sensitivity analysis procedure(Bergman & Lundberg, 2013). Figure 1 shows the impact of the criteria on each bank or alternative.

From the chart above, it can be seen that the biggest change in value is achieved by alternative 3 where, due to the decrease in the weight of the "liquidity" criterion, the increase in the weight of other criteria only further condition the conclusion reached and the budget shows that this bank shows the lowest risk of money laundering in the payment system as a support. the gray economy. Also, generally speaking, with other alternatives, the conclusion is that due to the increase in the weights of the criteria "efficiency", "profitability" and "solvency", their value increases, but still not enough to achieve greater value than alternative 2.

Conclusion

Everybody - individuals, politicians, experts, business people, every day considers and makes small and big decisions - decisions that affect individuals, families, business systems or social communities - regions, states and the whole world. In the most cases and problems that need to be solved there are multiple solutions. But the question that comes is which solution to choose? One who considers and makes a decision takes into account several aspects of the problem he is solving: some reasons speak in favor of making a decision in one way, but other reasons say that such a decision is reviewed and often revised.

Thus, the problem solving practices in the financial sector shows that they can be solved in different ways, respecting the relevant criteria. In the past years, considering the financial sector of the Republic of Serbia, there have been positive changes, which is confirmed by the parameters that indicates an increase in the efficiency of the banking system, growth of loans and deposits with banks, growth of capital market turnover, stimulation of household savings, etc. which has a positive effect on reducing the risk of money laundering and the grey economy. In order to achieve even better results, it is necessary to provide additional investment funds from clients, as well as to establish a network of monitoring clients' inflows and outflows of money, which will make decisions based on appropriate indicators that will be obtained by applying the best ways to measure bank performance which is certainly the responsibility of the National Bank of Serbia.

The application of decision support system combines the results of economic theory with the data provided by economic statistics. Key features of high-performing banks are reflected in providing high liquidity, maximizing profits, controlling costs and more. There are multiple approaches to measuring the performance of commercial banks. They all boil down to a larger or smaller selection of certain coefficients or ratios. Financial coefficients or indicators are representing relative ratios that need to give advance consideration to the degree of certainty that a bank will be able to monitor the balance of payments of deposits and placements.