Answers all parts in English

• Install sound-absorbing materials (such as acoustic panels, foam, or mineral wool) on the walls to reduce reverberation and sound transmission.
• Increase the thickness or density of the walls, or construct double walls with an air gap in between, which acts as a more effective sound barrier.

Reason: A convex mirror provides a wider field of view compared to a plane mirror. This means the manager will be able to see a larger portion of the hallway from the reception desk, thereby improving security and monitoring.

The color yellow is perceived because it reflects green and red light. When only green spotlights are turned on, the yellow shirt will only reflect the green component of the light, thus appearing green. There is no red light to be reflected, so the "yellow" component derived from red is not seen.