The depth at which the value of `g` becomes `25%` of that at the surface of the earth is (in `KM`)

Find the depth at which the value of g becomes 25% of that at the surface of the earth. (Radius of the earth = 6400 km)

At what height above the earth's surface does the value of g becomes 36% of the value at the surface of earth ?

At what height above the earth's surface does the value of g becomes 36% of the value at the surface of earth ?

A what height above the earth's surface the value of g becomes 25% of its value on the earth if radius of the earth is 6400km.