White Light Is Incident Normally on a Thin Soap Film

Multiple Choice

White light is incident normally on a thin soap film having an index of refraction of 1.34.It reflects with an interference maximum at 684 nm and an interference minimum at 570 nm with no minima between those two values.The film has air on both sides of it.What is the thickness of the soap film?

A) 766 nm
B) 627 nm
C) 638 nm
D) 894 nm
E) 510 nm