The classic millikan oil drop experiment was the first to

Question

Compute each part of following problem given below:

Problem: The classic Millikan oil drop experiment was the first to obtain an accurate measurement of the charge on an electron. In it, oil drops were suspended against the gravitational force by a vertical electric field.

Part I: Given that the oil drop is 0.85 m in radius and has a density of 910 kg/m³, find the weight of the drop in N

Part II: If the drop has a single excess electron, find the electric field strength needed to balance its weight.

I want you to clarify the physics in this above problem.