I would say all Desi Khutbas (the obligatory part in Arabic) with the Friday prayer included last 5 to 10 minutes. Have any classical scholars mentioned any minutes?
This khateeb whose khutbah and prayer together take ten minutes does not have deep understanding of Islam, rather he is ignorant, because understanding of the religion means keeping the khutbah short and making the prayer long, not effectively destroying them both!
http://www. islamqa .com/en/ref/112084