How can I make this sentence politer?
Hi. I have read this sentence:
And I was wondering how to make it politer. But I'm not sure if the particle の can be used after ます and I think, if I use the ます form I must change the だ by です too, to keep all the sentence polite.
So, my question is, which of these sentences are correct to make that sentence politer?
Thanks in advance.