At what depth below the surface of the earth, acceleration due to gravity g will be half its value 1600 km above the surface of the earth ?

At what depth below the surface of the earth, acceleration due to grav

1.	At what depth below the surface of the earth, acceleration due to gravity g will be half its value 1600 km above the surface of the earth ?
Answer» `4.2 XX 10^(6)` m `3.19 xx 10^(6)`m `1.59 xx 10^(6)` m None of the above ANSWER :A