In the STP protocol, assume that all switches are configured with the same priority. The MAC address of switch 1 is 00-e0-fc-00-00-40, and the MAC address of switch 2 is 00-e0-fc-00-00-10, the MAC address of switch 3 is 00-e0-fc-00-00-20, and the MAC address of switch 4 is 00-e0-fc-00-00-80, then the root switch should be ().

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