At what temperature can carbon reduce FeO to Fe and produce CO?

1. Lower than  400 oC

2. 400 oC

3. Higher than 600 oC

4. Higher than 400 oC

HINT: Carbon can reduce FeO to Fe and produce CO at temperature higher than 400oC
Explanation:
Any metal will reduce oxide of other metals which lie above it in the Ellingham diagram because free energy change will become more negative.
In the figure shown above point A : 
f G°C,CO < f GFe, FeO

Therefore, above point A, C reduces FeO to Fe forming carbon monoxide. Hence, reduction of FeO by carbon occurs above point A only.