Force and Energy $($Work Done$)???$

Below please find an equation of attractive force for a particle:

$F(r)=-\frac{e^{-r}}{r^3}$

where hat$(I)+-=1,$hat$(I{)}^2=\mathrm{.}001.$ The negative sign indicates that the force is attractive.

How much energy is needed to pull two of these particles apart from $r=0\mathrm{.}5$ to $r=5?$ Can you describe the amount of energy needed as they move apart from each other?

Well, an analytical solution may not be viable at this point. How about a numerical one?

Important Note:

Please do not worry about the units and get distracted by them. Just concentrate on the mathematical issue.