solve only 4, 5 and 6

In a lake, the population of a particular fish species is about 1 million. Fish reproduce by 20% of the population each month, regardless of the season. In addition, fish die naturally after living for an average of 10 months. There are two separate companies (for example, A and B) fishing with 5 boats on the edge of this lake. According to current data, each boat catches 5000 fish per month. However, if the total number of boats caught in the lake increases, the number of fish to be caught by each boat decreases, as the boats will prevent each other from fishing. In addition, if the fish population in the lake increases, the fish caught per boat increases, and if the population decreases, the fish caught per boat decreases. As companies earn money from hunting, they want to buy new boats over time and enlarge their boat fleet. 1. If you want to model this described system with 'System Dynamics', which variables would you use? How would you classify these variables as stock, flow and dummy variables? 2. Indicate the causal relationships in this system with arrows and signs. 3. Show the causality loops in this system, at least 1 negative, at least 1 positive, and at least 4 in total, and interpret the loops. 4. Draw the stock-flow model of this system. 5. Write down the equations (as much as possible) of the model you have drawn above. 6. Assuming the number of boats of the companies and the number of fish caught by each of the boats are constant, is the system in equilibrium? If not, in what direction is the system changing