A perfectly flat thin piece of glass (N=1.50) that is 6.00 cm long and and 2.0 cm wide is placed over a perfectly flat piece of black plastic (N=1.20) that is the same size. one end of the glass is slightly elevated while the other end is in contact with the plastic. Light of wavelength 600 nm is incident normally from above. One observes dark fringes at locations of 0.00cm, 1.0cm, 2.0cm, 3.0cm, 4.0cm, 5.0cm, and 6.0cm from the end that is in contact with the plastic. How thick is the air gap between the glass and plastic at the elevated end of the glass?