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
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.