Suppose an attractive nuclear force acts between two protons

Suppose an attractive nuclear force acts between two protons which may be written as $\mathrm{F}=\mathrm{ce} \mathrm{ekr}^{-\mathrm{r}}{ }^{2}$.

(a) Write down the dimensional formulae and appropriate SI units of C and $\mathrm{k}$

(b) Suppose that $k=1$ Fermi and that the repulsive electric force between the protons is just balanced by the attractive nuclear force when the separation is 5 Fermi. Find the value of $C$.