It asks "Which scripture is the source of a verse A?"
This question asks "Which scripture is the source of a verse B and who composed it?"
Now, verse A and B both are part of a same Stotra, with verse A the 1st verse and verse B the 5th verse of a Saraswati Storam (a Hymn), which was composed by Agastya Muni.
So, both these questions will have the same answer, if the Stotra is at all part of some scriptures. (the author part is already answered by me under Q- B, and the OP of Q-A is not asking about author at all)
The answer of both the questions will be just one viz-something like " Yes, it's part of XYZ Purana or some other scripture"
Question: So should they be considered as duplicates? (Question A should be marked as a duplicate of Question B)
The answer given uses the following questions as examples:
Who is the father of Kumara Swamy and Ganesha?
Who is the husband of Parvati Devi?
Now, these questions are entirely different questions. None can mark them as duplicates.
In this case, however, both the questions are "exactly" the same. The question basically is:
"In which scripture is found Agastya Krutha Saraswati Stotram?"
Assume, there is a Stotram comprised of 50 verses. Are we going to allow 50 such different questions that are just asking, separately, "What is the source of verse 1 to 50?"