What is the value of acceleration due to gravity at a height equal to half the radius of the Earth, from its surface ?

When a planet revolves around the Sun, in general, for the planet

Electrical as well as gravitational affects can be thought to be caused by fields. Which of the following is true for an electrical or gravitational field?

Two bodies of masses $$8 \mathrm{~kg}$$ are placed at the vertices $$A$$ and $$B$$ of an equilateral triangle $$A B C$$. A third body of mass $$2 \mathrm{~kg}$$ is placed at the centroid $$G$$ of the triangle. If $$A G=B G=C G=1 \mathrm{~m}$$, where should a fourth body of mass $$4 \mathrm{~kg}$$ be placed, so that the resultant force on the $$2 \mathrm{~kg}$$ body is zero?