In [Shemot 19:7](http://www.chabad.org/library/bible_cdo/aid/9880#showrashi=true&v=7) Moshe summons the elders and relays God's commands, and then in the next verse it says that *all the people* responded:

> וַיָּבֹא משֶׁה וַיִּקְרָא לְזִקְנֵי הָעָם וַיָּשֶׂם לִפְנֵיהֶם אֵת כָּל הַדְּבָרִים הָאֵלֶּה אֲשֶׁר צִוָּהוּ יְהוָֹה:  
וַיַּעֲנוּ **כָל הָעָם** יַחְדָּו וַיֹּאמְרוּ כֹּל אֲשֶׁר דִּבֶּר יְהוָֹה נַעֲשֶׂה וַיָּשֶׁב משֶׁה אֶת דִּבְרֵי הָעָם אֶל יְהוָֹה: 

> Moses came and summoned the elders of Israel and placed before them all these words that the Lord had commanded him.  
And all the people replied in unison and said, "All that the Lord has spoken we shall do!" and Moses took the words of the people back to the Lord.

I'm trying to understand who responded.  I think that usually כָל הָעָם (all the people) means *all* the people, but here Moshe has only summoned the elders.  So does the "all" here mean the elders, perhaps answering *on behalf of* all the people?  Or was there a gap between the verses in which the elders relay the message to the people and gain their ascent, which nonetheless happens in unison?  Or was this said in front of everybody -- Moshe summoned the elders to him but this was in the hearing of everybody and they jumped in to respond?

Rashi doesn't say anything about this point, nor did any of the chumashim we had at the table at torah study this morning where this question came up.

I'm not asking about  נַעֲשֶׂה וְנִשְׁמָע a few chapters later, but specifically about the exchange before *matan torah*.