70. Solving a chemistry problem

4. Based on available data:
C (graphite) 2F2 (r) \u003d CF4 (r), ΔG ° 298, xp \u003d -636.04 kJ
C (graphite) 2 Cl2 (r) \u003d CCl4 (r), ΔG ° 298, xp \u003d -60.63 kJ
C(graphite) 2 Br2(l) = CBr4(g), ΔG°298, xp = 66.94 kJ,
C (graphite) 2I2 \u003d CI4 ΔG ° 298, xp \u003d 124.86 kJ,
determine: a) the possibility of obtaining carbon tetrahalides from simple substances at standard conv.; b) change in the degree of affinity of halogens for carbon; c) which of the tetrahalides is the most stable at st.