A flat sheet of ice (n = 1.309) has a thickness of 1.8cm. It is on top of a flat sheet of crystalline quartz (n= 1.544) that has a thickness of 0.94 cm. Light strikes the ice vertically and travels through it and then during the quartz. In the time it takes the light to travel through the two sheets, how far (in cm) would it have travelled in a vacuum?