Compute all parts of given question:
Question: An 18.5-g mass is suspended 4.97 cm above a nonconducting flat plate, directly above an embedded charge of q.
Part A: If the mass has the same charge, q, how much must q be so that the mass levitates (just floats, neither rising nor falling)?
Part B: If the charge q is produced by adding electrons to the mass, by how much will the mass be changed?
Please explain clearly with details so that I can follow.