What are the inferred pressure and temperature at the boundary of Earth's stiffer mantle and outer core? 
A) 1.5 million atmospheres pressure and an interior temperature of 4950°C 
B) 1.5 million atmospheres pressure and an interior temperature of 6200°C 
C) 3.1 million atmospheres pressure and an interior temperature of 4950°C 
D) 3.1 million atmospheres pressure and an interior temperature of 6200°C