Answer
$$a=25.1\space \text{in}$$
Work Step by Step
For a circle of radius $r$, the arc length $s$ corresponding to a central angle $\theta$ (in radians) is given by $s=r\theta$.
Therefore,
$$a=(6\space \text{in})\bigg(\dfrac{4\pi}{3}\bigg) = 8\pi\space \text{in} = 25.1\space \text{in}$$
