Thank you for the opportunity to help you with your question! Hope your day is going well!

I just realized I should not have accepted this question, you did not provide all the information for the problem. You need a piece of information about the countries A or about the countries B. What you need to do is we know that the combined countries of A & B is 153,973...this is represented as

A+B=153,975 km

If you give me the rest of the details, I will give you the full solution. I am sorry for accepting, and please do not leave a bad review. Just give the rest of the details, and I will gladly help.

Please let me know if you need any clarification. I'm always happy to answer your questions. Leave a positive review if you are happy!