Ive been asked to modify an existing DNS record. I needed to change the IP address associated with the A record for xyz.com from 72.45.12.173 to 150.12.172.9. I made the change but when I attempt to test name resolution from my workstation, xyz.com is still resolving to 72.45.12.173.

a. what is a reason this condition might exist?

b. what change could I make to my local workstation to work around this issue?

c. How could I keep this problem from happening next time If I need to make a similar DNS change?