A student measures the electric field at a distance r from the center of a small isolated conducting sphere to be E=(2.5±0.2)×103N/C. The distance is measured as r=(0.80±0.02)m. Using these data, which of the following best estimates the percent uncertainty in the calculated charge on the sphere?
a) 10\%
b) 13\%
c) 8\%
d) 9\%