A coin is covered by a sheet of glass refractive index n11.50 and thickness t1 2cm On top of this is placed a further sheet of thickness t2 4cm and unknown refractive index n2 The coin appears d 2.25c?

the FULL question is http://wiki.answers.com/Q/A_coin_is_covered_by_a_sheet_of_glass_refractive_index_n11.50_and_thickness_t1_2cm_On_top_of_this_is_placed_a_further_sheet_of_thickness_t2_4cm_and_unknown_refractive_index_n2_The_coin_appears_d_2.25cm above its real position to an observer who views it in a near normal direction through the two sheets of glass. what is the refractive index of the 2nd sheet? pleasee HELP me answer this! i am so stuck!!