A team evaluating sustainable packaging wants to estimate the proportion of retail brands that use biodegradable materials in their products. Find the minimum sample size required for this estimate, assuming a $95\%$ confidence level and a margin of error of $0.10$. Earlier research indicates that around $70\%$ of retail brands have adopted biodegradable packaging.

• A. $93$
• B. $81$
• C. $67$
• D. $75$

Answer: (B)