[填空题]
What is the linear spe6 bf /dbq69tt gi.zhb8ed7 nh6 76hev qltc3z 8i6skf:gh of a point (a) on the equator, $m/s$ (b) on the Arctic Circle (latitude 66.5$^{\circ} $ N), $m/s$ (c) at a latitude of 45.0$^{\circ} $ N, due to the Earth’s rotation? $m/s$