1)
Why does it say "va'Ya'anu" and also "Leimor"?
1.
Ohr ha'Chayim #1: Many people do not speak at once. One spoke on behalf of all of them.
2.
Ohr ha'Chayim #2: This teaches that they did not agree like they said initially. In the end, [Efron] demanded the full price.
3.
Ha'amek Davar: They resolved what to answer, and sent one of them to tell him their answer.