Answer
The percent uncertainty is about 14.4%.
Work Step by Step
When we multiply measurements, we can simply add the percent uncertainties.
We know that the percent uncertainty of the radius is $\frac{0.04}{0.84}\times 100\% = 4.8\%$.
When we calculate the volume, we use $r^3$. Therefore, we should add the percent uncertainty three times.
Therefore, the percent uncertainty is $3\times 4.8\% = 14.4\%.$