Step 1: A confidence interval for a proportion is always constructed symmetrically around the point estimate \(\hat{p}\), running from \(\hat{p} - E\) to \(\hat{p} + E\), where \(E\) is the margin of error.
Step 2: Because the interval is symmetric, the point estimate \(\hat{p}\) is simply the midpoint of the given interval.
\[ \hat{p} = \frac{0.241 + 0.561}{2} = \frac{0.802}{2} = 0.401 \]
Step 3: So the best point estimate of the true proportion of employees preferring plan A is \(0.401\).
The correct answer is (C) 0.401.