Answering Amen After the Birchos Hageulah

"ויאמר ה' אל משה כבד לב פרעה מאן לשלח העם" (יד ז)

מאן are the same letters as אמן to allude that the reason that we have not yet merited the full Geulah is because we are not sufficiently strict to answer amen and as it says in Sefer Hagan Vederech Moshe (Day 11) that the Geulah is taking a long time because we are not careful to answer amen to the brachah of "Hamachazir Shechinaso LeTzion" – because we are in a hurry to recite the Modim D’Rabbanan that follows, and to the brachah of "Haporess Succas Shalom...V’Al Yerushalayim" said on Friday night – because we are hurrying to start "Veshomru" right after. (Yoshia Tzion)