Light Is Incident Perpendicularly from Air onto a Liquid Film $199 \mathrm {~nm}$

Light is incident perpendicularly from air onto a liquid film that is on a glass plate. The liquid film is $199 \mathrm {~nm}$ thick, and the liquid has index of refraction $1.60$ . The glass has index of refraction 1.50. Calculate the Iongest visible wavelength (as measured in air) of the light for which there will be totally destructive interference between the rays reflected from the top and bottom surfaces of the film. Assume that the visible spectrum lies between $400 \mathrm {~nm}$ and $700 \mathrm {~nm}$ .