Compute each part of given problem:

Problem: A straight, non conducting plastic wire 9.00cm long carries a charge density of 125nC/m distributed uniformly along its length. It is lying on a horizontal tabletop.

Part I: Find the magnitude and direction of the electric field this wire produces at a point 4.00cm directly above its midpoint.

Part II: If the wire is now bent into a circle lying flat on the table, find the magnitude and direction of the electric field it produces at a point 4.00cm directly above its center.

Show how you get the answer, so that I can better understand how to do it.