Dimensional formula of \[\frac{{{e}^{4}}}{{{\varepsilon }_{0}}^{2}{{m}_{p}}{{m}_{e}}^{2}{{c}^{2}}G}\] is: (where e = charge, \[{{m}_{p}}\]and \[{{m}_{e}}\], are masses \[{{\varepsilon }_{0}}=\] permittivity of free space, c = velocity of light and G = gravitational constant):