The images $($A$,$ B & C$)$ below are all taken from a screen during a double slit experiment.

If the total width of the pictures is $0\mathrm{.}04$ meters $($from left to right$),$ and the screen is $2$ meters from the slits, what is the separation of the slits in B$?($We are using $500$ nm light.$)$ Answer in mm to within $1\%$ of the correct answer.