a. 9.0 x 10^3 N/C

b. 1.8 x 10^4 N/C

c. 2.4 x 10^4 N/C

d. 3.6 x 10^4 N/C

e. 1.4 x 10^5 N/C

The sphere has a radius of .5 m, so shouldn't the electric field be calculated from (1.5 m), which is the distance of the nearest excess charge to the point? Why must we calcuate taking r as 2.0 when there is no charge at the point in the center of the sphere?

Taking r to be 1.5, I get an answer of approx. 1.6 x 10^4 N/C

Thank you for your help.