A curve segment $,$ defined by the equations $,,$ and $,,$ is located in space. This curve segment carries a total charge uniformly distributed along it$.$

a$)$ Write the explicit expression for the volume charge density corresponding to this charge distribution.

b$)$ Calculate the electric field at the point $.$

c$)$ Compute separately the force exerted on a point charge $,$ placed at $,$ by the total charge on the curve segment $,$ and the force exerted by the point charge on the charge distributed along the curve $.$ Discuss the results.