Light of Wavelength 425

Multiple Choice

Light of wavelength 425.0 nm in air falls at normal incidence on an oil film that is 850.0 nm thick.The oil is floating on a water layer 15 cm thick.The refractive index of water is 1.33,and that of the oil is 1.40.You want to add oil so that light reflected off of the top of the oil film will be canceled.What is the minimum distance that you should INCREASE the oil film?

A) 60.7 nm
B) 75.9 nm
C) 106 nm
D) 121 nm
E) 152 nm