In STP, assuming that all switches are configured the same priority, switch1 MAC address is 00-e04c-00-00-40, switch 2 MAC address is 00-e0-fc-00-00-10, switch3 MAC address is 00-e0-fc-00-00-20, switch4 MAC address is 00-e0-fc-00-00-80, the root switch should be ( ).

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