Solve the given parts of following problem:
Problem: A sheet of an unknown material that is 1.223 + or - .003 micro meters thick is suspended in air. In reflected light, there are gaps in the visible spectrum at 421, 474, 542, and 633 nm.
Part A: Draw a picture of the setup and include a ray diagram of the interference off of the sheet.
Part B: Find a good estimate of the index of refraction of the material.
Please show work I think I have the answer just not positive.