The composition of the solid phase at equilibrium at 200 degrees Celsius cannot be determined without additional information on the phase diagram or the specific alloy system.
The composition of the solid phase at equilibrium at a given temperature depends on the alloy system and its phase diagram. The phase diagram provides information about the phases present at different temperatures and compositions.
Without knowing the specific details of the alloy system and its phase diagram, it's not possible to determine the composition of the solid phase at equilibrium at 200 degrees Celsius.
If you have the phase diagram for the alloy system in question, you would need to locate the temperature of 200 degrees Celsius on the diagram and examine the corresponding composition of the solid phase at that temperature.
In summary, to determine the composition of the solid phase at equilibrium at 200 degrees Celsius, you would need information from the alloy's phase diagram or additional details about the alloy system.