Official Solution: If 25% of a company's employees donate at least 4% of their salary to the Charity Fund, what percentage of the company's employees donate at least 5% of their salary to the Charity Fund? Let:
\(x\%\) donate less than 4%;
\(y\%\) donate at least 4% but less than 5%;
\(z\%\) donate at least 5%.
Observe that these groups do not intersect and \(x+y+z=100\).
Given: \(y+z = 25\%\). Question: \(z=\)?
(1) 20% of the company's employees donate at least 4% but less than 5% of their salary to the Charity Fund.
Given: \(y=20\%\). Therefore, \(y+z=20+z=25\%\), which results in \(z=5\%\). Sufficient.
(2) 95% of the company's employees donate less than 5% of their salary to the Charity Fund.
Given: \(x+y=95\%\). Therefore, \(x+y+z=95+z=100\%\), which results in \(z=5\%\). Sufficient.
Answer: D