- 68% of the widget weights lie between 53 and 75 ounces.
- The percentage of widget weights between 31 and 75 ounces is 84.0%.
- The percentage of widget weights below 86 ounces is 97.72%.
\boxed{
\begin{align_}
\text{a)} & \quad 53 \text{ and } 75 \\
\text{b)} & \quad 84.0\% \\
\text{c)} & \quad 97.72\%
\end{align_}
}