The coherent green light of wavelength 650 nm illuminates two narrow slits in a screen. The slits are separated by 0.08 mm. A thin transparent plastic film (index of refraction 1.3) covers one slit. The light from the slits reaches a screen 1.0 m away. Starting from first principles, find the minimum thickness of the film that turns the third-order dark fringe (without the film) into a bright fringe (with the film).