Critical Reasoning (CR) | Re: Within the earth's core, which is iron, pressure increases with depth.

Premise :
Pressure within the earth's iron core increases with depth. Because the melting temperature of iron increases with pressure, the inner core is solid and the outer core molten. Physicists can determine iron's melting temperature at any pressure and the pressure it is under at any depth.

Pre-thinking :
What further premise, combined with the information provided, would support the conclusion that physicists can determine the temperature at the boundary between the outer and inner cores?
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