Gravitation

A man of mass $m$ starts falling towards a planet of mass \(M\) and radius \(R\). As he reaches near to the surface, he realizes that will pass through a small role in the planet. As he enters the role, we sees that the planet is really made of two pieces a spherical shell of negligible thickness of mass \(3 M / 4\) and a point mass \(M / 4\) at the centre. Change in the force of gravity experienced by the man is