Help please and thank you

Scenario: A medium$-$sized company with three departments $($HR$,$ Sales, IT$)$ has each department on a separate subnet. The company uses a single router for inter$-$departmental communication and external connectivity.

Routing Consideration: Given the scenario, explain how the router ensures data packets from the HR department reach the IT department.

NAT Application: If the company's entire network accesses the internet using a single public IP address, how does NAT ensure proper communication without conflicts?