Question

Which version of the sentence is using commas correctly?

I must say Rebecca, this case is puzzling.
I must say Rebecca this case, is puzzling.
I must say, Rebecca this case is puzzling.
I must say, Rebecca, this case is puzzling.

Answer 1

I think the it is the last one though but I am not sure it is correct

Answer 2

The last one

I must say, Rebecca, this case is puzzling.