Two very long, parallel wires are separated by d $=0\mathrm{.}085$ m$.$ The first wire carries a current of I$1=0\mathrm{.}85$ A$.$ The second wire carries a current of I$2=0\mathrm{.}75$ A$.$ Express the magnitude of the force between the wires per unit length, f$,$ in terms of I$1,$ I$2,$ and d$.$ Calculate the numerical value of f in N$/$m$.$

Is the force repulsive or attractive?

Express the minimal work per unit length needed to separate the two wires from d to $2$d$.$

Calculate the numerical value of w in J$/$m$.$