A thin disk of radius 1.2m has a uniform surface charge density = 0.0030 C/m. (a) (2 points) What is the total charge on the disk? (b) (5 points) You are asked to calculate the electric field at three points along the axis that goes through the center of the disk and is perpendicular to the disk: point A is 1.0 cm from the disk. Point B is 1.0 m from the disk, and point C is 10 m from the disk. Explain the formulas you could justify using to calculate the field at A, which is appropriate for B, and which could be used for C. (Hint: You should attempt to show off your physics skills by using a different formula for each point! But note, you don't need to do any of the calculations. Just pick and explain.)