Assume Newton's theory of gravitation to hold true for the following. What should be the mass of a uniform sphere of radius \(R\) so that the escape velocity from its surface equals \(c,\) the velocity of light in vacuum?
1. \(\frac{Rc^2}{G}\)
2. \(\frac{Rc^2}{2G}\)
3. \(\frac{2Rc^2}{G}\)
4. \(\sqrt2\frac{Rc^2}{G}\)