I got many correct answers, thanks to all who responded. This was a “simple” application of pythogoras theorem. I got correct answers from Abhinav Jain, Pratik Poddar, Karan, Praneeth Ruthala, Suman Saraf and Mahi Saraf. While everyone sent me only the answer, I received a full solution from Mahi, which I am reproducing as it is – thanks Mahi!
The answer is 27,000. Please note that there is a very minor omission in Mahi’s answer at one place, where she meant to write 6^2 instead of 6.
Hope you all enjoyed the puzzle!