Question: Upon receiving a Floor Idle message from the floor control server arbitration logic, what action(s) does the floor control interface towards the MCPTT client take regarding the message's subtype and state transition?
Option 1: Always sets the first bit in the subtype to '0' (Acknowledgment not required) and enters the 'U: permitted' state.
Option 2: May set the first bit in the subtype to '1' (Acknowledgment is required) but does not change its state.
Option 3: May set the first bit in the subtype to '1' (Acknowledgment is required) and shall enter the 'U: not permitted and Floor Idle' state.
Option 4: Shall set the first bit in the subtype to '0' (Acknowledgment not required) and enters the 'U: not permitted and Floor Idle' state.
Explanation: This is correct because, according to the specifications, upon receiving a Floor Idle message, the interface has the option (may) to set the first bit in the subtype to '1', indicating that an acknowledgment is required. Additionally, it must (shall) transition into the 'U: not permitted and Floor Idle' state, aligning with the detailed protocol for managing floor control and acknowledgments in MCPTT interactions with LMR systems.