Three elementary steps are proposed for a laboratory synthesis:
(1) A +B → C ΔG∘=+25kJ mol−1
(2) C → D ΔG∘=−10kJ mol−1
(3) D → A +E ΔG∘=−20kJ mol−1
If all three steps proceed exactly as written, what is the standard free-energy change for the overall conversion of B to E?
a) +35kJ mol−1
b) −5kJ mol−1
c) −30kJ mol−1
d) +15kJ mol−1