This is an example of simple past usage I stumbled upon on YouTube :

"Sarah and David talked for two hours"

It is not clear to me why present perfect or past continuous are not used here instead of past simple or can all of these tenses be used correctly? "For two hours" specifies a duration of time and "for" is also a signal word used in present perfect tense and past continuous tense. I thought past simple is used for finished actions, but in this example, the action was in progress. So why is this sentence correct in simple past tense?

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Comments  (Page 2) 
CJ Sir, I understand. Thanks a lot for this valuable note.