A long, straight line charge with charge per unit length extends along the z -axis from a to .Another line charge with -

A long, straight line charge with charge λ  per unit length extends along the z -axis from a to ∞ .Another line charge with -λ per unit length is placed along the -z -axis from -a to -∞.

(a) By direct integration determine the electrical potential in cylindrical coordinates. 

(b) Find the r component of the electric field