In a vemier callipers the main scale and the vernier scale are made up different materials. When the room temperature increases by `Delta T^@ C` , it is found the reading of the instrument remains the same. Earlier it was observed that the front edge of the wooden rod placed for measurment crossed the `N^(th)` main scale division and (N + 2) msd coincided with the 2nd vsd. Initially, 10 vsd coincided with 9 msd. If coefficient of linear expansion of the main scale is `alpha_1` and that of the vermier scale is `alpha_2` then what is the value of `alpha_1//alpha_2` ? (Ignore the expansion of the rod on heating)