Black Hole Questions

The condition for a uniform spherical mass $m$ of radius $r$ to be a black hole is [$G=\text{gravitational constant}$ and $c=\text{speed of light}$ ]:

A black hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass = $5.98\times 10^{24}\text{kg}$) have to be compressed to be a black hole?