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B.1 Problem

We are going to design and to implement a distributed program that simulates the behavior of a banking system:

• every node of the network holds a money deposit, and
• every node may randomly withdraw money from its deposit and send it to some neighbor node which stores the money in its own deposit.

Let the network value be the sum of all money stored in some node or contained in some message of the network; by above operation this value remains constant but is unknown to every node.

The program is to determine the network value in every node without interrupting normal operation; when the value is known to every node, execution may terminate. An assertion should check whether the result is correct.