Physics · Gravitation

A particle of mass m is placed in four different situations: (I) Inside a uniform spherical shell of mass M, but not at the center. (II) Inside a uniform spherical shell of mass M, at the center. (III) Outside a uniform spherical shell of mass M, at a distance r from the center. (IV) Outside a uniform solid sphere of mass M, at a distance 2r from the center. Rank these situations according to the magnitude of the gravitational force on the particle, from least to greatest.