Solve the all parts of given problem:
Problem: A 24.5-g mass is suspended 3.21 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 give me an explanation for above problem.