Answer
$r \times a = 0$
Work Step by Step
The vector $r$ is directed from the center of the circle to the person.
The vector $a$ is directed from the person to the center of the circle.
The angle $\theta$ between these two vectors is $180^{\circ}$
We can find $r \times a$:
$r \times a = r~a~sin~180^{\circ} = 0$
