White Light Is Shone on a Very Thin Layer of Mica

Multiple Choice

White light is shone on a very thin layer of mica (n = 1.57) .When the mica layer is observed from the illuminated side,interference maxima for wavelengths of blue (480 nm) and yellow (560 nm) are observed.What is the thickness of the mica layer?

A) 1.58 $\mu$ m
B) 0.79 $\mu$ m
C) 3.16 $\mu$ m
D) insufficient information is given.