A spherical cavity is made in a lead sphere of radius R such that its surface touches the outside surface of the lead sphere and passes through its centre. The mass of the lead sphere before hollowing was M. The force of attraction that this sphere would exert ona particle of mass m, which lies at a distance d from the centre of the lead sphere on the straight line joining the centres of the sphere and the centre of the cavity as shown in the figure is

Options

A. `(GMm)/(2R^2) hati`
B. `-(GMm)/(2R^2) hati`
C. `-(GMmd)/(2R^3) hati`
D. `(GMm(R/2-d))/(R^3) hati`

Answer

B