seta $=R($ for $my$ smenty$)$

A charged ring with radius a with uniform linear charge density $$ lies in the $xy$ plane, with the origin of coordinates at the center of the ring. A finite straight line charge of length $L$ and uniform charge density ${}^{\text{'}}$ is located on the $z$ axis, with its lower end a distance $d$ away from the center of the ring.

$($a$)(15$ pts