In separating carbon$-12$ and carbon$-14$ a sample containing both of them is first singly ionized and then accelerated from rest through a potential difference $V.$ This beam then enters a magnetic field $B$ at right angles to the field and is bent into a semi$-$circle. A particle detector at the end of the path measures the amount of each isotope. Given that the magnetic field is $0\mathrm{.}050$ T $,$ what must be the accelerating potential $V$ so that these two isotopes will be separated by $4\mathrm{.}00$ cm at the detector? $($Make sure you have the right answer and explain this is a grade $12$ question so solve it using grade $12$ physics$).$