I'm currently doing a value chain diagram for a business that runs service centers repairing digital products and hardware.

The service center is operated by engineers that would diagnose the customer's product and advice accordingly what needs to be done.

The business have a warehouse to store buffered parts and also have company van to provide transportation for parts or deliveries if needed.

The business runs service centers in Singapore, Indonesia, Myanmar and the Philippines. When a customer comes to the service center, the customer would be required to take a queue number from the automated kiosk to wait for their turn. Once ready, the engineer on site would first diagnose the product and advice the customer what would be required to solve their issue. If the customer agrees and decides to proceed, their product would be taken in and the customer would be contacted once the product is ready to be collected. The customer can request for a delivery at a charge or they could do self-collection.

What would be defined as the "Operations" for this company in detail?

What would be good "Marketing and Sales" for this company in detail?