Refer to the exhibit. Users from the Engineering VLAN complain that every time Business VLAN users have a network connectivity issue， the Engineering VLAN users usually have problems experiencing slow response or network connectivity problems. After troubleshooting， an unauthorized switch 2 was found. This unauthorized switch has been a regular problem， assuming the root bridge function under the spanning-tree domain and causing the Engineering VLAN to be unstable. Which three of these actions could be suggested to fix the problem？（）