The atomic radii of a divalent cation and a monovalent anion are $0\mathrm{.}73nm$ and $0\mathrm{.}136nm,$ respectively.

$($a$)$ Calculate the force of attraction between these two ions at their equilibrium interionic separation $($i$.$e$.,$ when the ions just touch one another$).$

i

$N$

$($b$)$ What is the force of repulsion at this same separation distance?

$N$