Answer
See below
Work Step by Step
Plug the height in for $h$ and the radius in for $r$.
The efficiency ratio for a soup can: $\frac{S}{V}=\frac{2(3.4+10.2)}{3.4\times10.2}\approx0.784$
The efficiency ratio for a coffee can: $\frac{S}{V}=\frac{2(7.8+15.9)}{7.8\times15.9}\approx0.382$
The efficiency ratio for a paint can: $\frac{S}{V}=\frac{2(8.4+19.4)}{8.4\times19.4}\approx0.341$
