The position of an object moving along the x-axis is given by, \(x=a+bt^2\)  where \(a=8.5\) m, \(b=2.5\) ms^-2, and \(t\) is measured in seconds. Its velocity at \(t=2.0\) s will be:
1. \(13\) m/s
2. \(17\) m/s
3. \(10\) m/s
4. \(0\)