A laser beam passes through a slit that is \(1500 \mathrm{~nm}\) wide. In the interference pattern created on a distant screen, the angular positions of the two first-order dark fringes are \(\pm 25. 0^{\mathrm{a}}\). The beam then is shone on a soap film \(\left(n_{\text {film }}=1.40\right)\) floating on water \(\left(n_{\text {water }}=1.33\right)\). What is the minimum film thickness that causes light reflected at normal incidence from the air-film interface to cancel light reflected at normal incidence from the film-water interface?