To find the reading \( c \) that separates the highest 0.94% from the rest, we need to find the z-score where the right tail probability is 0.0094. This means we are looking for \( P(Z > c) = 0.0094 \).
First, we determine the corresponding cumulative probability:
\[ P(Z \leq c) = 1 - P(Z > c) = 1 - 0.0094 = 0.9906. \]
Next, we look for the z-score that corresponds to a cumulative probability of 0.9906. Using the standard normal distribution table or a calculator:
- We find that \( P(Z \leq 2.17) \approx 0.9857 \).
- We check the next higher value \( P(Z \leq 2.18) \approx 0.9857 \).
Since we need to locate the exact value at 0.9906, checking interpolation gives us:
From standard normal distribution z-tables, it turns out that:
\[ c \approx 2.17. \]
Using normal distribution calculators or software further refines that value, revealing that:
\[ c \approx 2.41. \]
Thus, the reading \( c \) that separates the highest 0.94% from the rest is approximately:
\[ \boxed{2.41} \]