What is the ruling on the prayer of the Imam and the congregants if the Imam forgot and prayed three rak'ahs in 'Asr then the congregants reminded him, or he prayed five rak'ahs in Dhuhr and no one reminded him until after the Tasleem?

If the Imam forgets the last unit (rak'ah) of the Asr prayer and is reminded by the congregants after the Tasleem (salutation of peace), he should intend to complete the prayer, perform the missing unit, and then prostrate for forgetfulness (sujud al-sahw). This is on the condition that there has not been a prolonged interval that would prevent making up the unit, such as leaving the mosque or remaining for an customarily long period.