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-- Tx1
In[1]:  alex sends 1 coin
Out[1]: mike receives 1 coin
Tx1 is signed by alex

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-- Tx2
In[1]:  alex sends 2 coin
Out[1]: mike receives 1 coin
Out[2]: rose receives 1 coin
Tx2 is signed by alex

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-- Tx3
In[1]:  rose sends 1.2 coin
Out[1]: alex receives 1.1 coin
Tx3 is signed by rose
Tx3 is signed by mara