Hi everyone please see the problem below:

Im trying to learn how to evaluate 3a. NOTICE: ap is a vector(boldfaced). My prof vagely mentioned something about not being able to integrate directly since as the direction of phi chances so does the direction ap. I know this seems unclear as this has me confused aswell and i cant find any information in my text regarding this. Can someone please help me understand how to integfrate this?

(p, phi , z)

p = radial distance from z-axis

phi = angle in radians meansured from "x-axis"

z=z as in cartesian.

Thank you!