Gravitational pull on an object on earth surface is $\displaystyle \frac{GmM_E}{R_E^2}$ which equals 630N(1)
$\displaystyle m$ is the mass of object
$\displaystyle M_E $is the mass of the Earth
$\displaystyle R_E$ is the radius of earth
$\displaystyle G$ is the gravitational constant
Regarding the body you mentioned,
Gravitational pull on an object on the body is $\displaystyle \frac{Gm(M_E/3)}{(R_E/2)^2}$
Use (1) to help you find the answer
