b
The gravitational potential \(V\) at a point distance \('r'\) from a body of mass \(m\) is equal to the amount of work done in moving a unit mass from infinity to that point.

\({V_r} - {v_ \propto } =  - \int\limits_ \propto ^r {\overrightarrow E .d\overrightarrow r }  =  - GM\left( {1/r - 1/ \propto } \right)\)

\( = \frac{{ - GM}}{r}\left( {As\,\overrightarrow E  = \frac{{ - dv}}{{dr}}} \right)\)

\((i)\) In the first case 

\(when\,{v_ \propto } = 0,\,{V_r} = \frac{{ - GM}}{r} =  - 5\,unit\)

\((ii)\) In the second case \({v^ \propto } =  + 10\,unit\)

                                         \({V_r} - 10 =  - 5\)

or                                      \({V_r} =  + 5\,unit\)