I gave my first attempt with the following optionals in 2016,

Physics (127)
International Law (76)
Journalism (62)
Gender Studies (50)
Town Planning (18)

Apart from Physics, I prepared all optionals in about 10 days each. I want to replace Town Planning with US History or Public Administration. Which one would be easier and less time consuming given the fact that I haven't touched these subjects at all and have no basic idea about it?

Secondly, if I replace two optionals and go for International Relations, how much time approximately would it take to cover the entire course? Would it be manageable in about 30 days?