In a circle with a radius of 21 5/8 yd, an arc is intercepted by a central angle of 5pi/6 radians... What is the arc length?

The answer is a because i went through all the other ones that it didn’t come out right

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .