Two masses exert a force of 1,161 N on each other when they are 20 km apart. How much force will these two masses exert on each other when they are 40 km apart?

The star betelgeuse is about 600 light-years away. if it explodes tonight, a. we'll know because debris from the explosion will rain down on us from space.b. we'll know it immediately because it will be brighter than the full moon in the sky.c. we won't know about it until 600 years from now.d. none of the above.