Four points are located with respect to the Earth's surface as follows:
A: at an altitude h=20RE,
B: at an altitude h=10RE,
C: at a depth d=25RE, and
D: at a depth d=15RE,
where RE is the mean radius of the Earth.
Answer the following questions, taking g to be the acceleration due to gravity at the Earth's surface.
(i) Arrange the magnitudes of gravitational acceleration at the four points in descending order.
(ii) Justify your ranking qualitatively without using numerical calculation, referring only to how g varies with altitude and with depth.
(iii) Between points B and C, which one will experience the larger fractional change in g relative to the surface value? Explain briefly.