Inverse and Direct Variation Word Problems - Examples

The famous equation: $E = mc^{2}$ is "Einstein's mass-energy equivalence". $E$ is the energy of an object; $m$ is the mass of the object; $c$ is the speed of light, which is a constant. In other words, Einstein found out that mass is just energy that is very VERY compressed. Einstein's equation led to whole new discoveries like nuclear power.

Which of the following is true about Einstein's equation?