At about 10 s after the Big Bang, the universe had cooled to a temperature of approximately

Question:

At about 10"" s after the Big Bang, the universe had cooled to a temperature of approximately 1013 K.
(a) Calculate the thermal energy kKT of the universe at that temperature.
(b) Explain what happened to most of the hadrons-protons and neutrons-at that time.
(c) Explain what happened to electrons and positrons in terms of temperature and time.