Answer
We can rank the points according to the value of the free-fall acceleration:
$b = d = f \gt e \gt c \gt a$
Work Step by Step
We can use Equation (13-14) to write an expression for the free-fall acceleration $g$:
$g = a_g-\omega^2~R$
$a_g = \frac{GM}{r^2}$
$\omega$ is the angular speed as the planet rotates
$R$ is the radius of rotation
At the poles, $R = 0$
Therefore, at the poles: $~~g = a_g$
At the equator, $R$ is the planet's radius.
$\omega$ is fastest for the planet that rotates in $16~h$ and slowest when the planet rotates in $48~h$
We can rank the points according to the value of the free-fall acceleration:
$b = d = f \gt e \gt c \gt a$
