It is postulated that the radial electric field of a group of charges falls off as E_r = C/rⁿ, where C is a constant, r is the distance from the center of the group, and n is an unknown exponent. To test this hypothesis, you make a field probe consisting of two needle tips spaced 1.00 mm apart. You orient the needles so that a line between the tips points to the center of the charges, then use a voltmeter to read the potential difference between the tips. After you take measurements at several distances from the center of the group, your data are as follows:

Distance (cm)....................Potential difference (mV)
2.0 ..................................................34.7
4.0 .................................................. 6.6
6.0 .................................................. 2.1
8.0 .................................................. 1.2
10.0. ................................................0.6

Use an appropriate graph of the data to determine the constants C and n.