**Answer:**

Approximately 95% of the numbers of days will be between 26 and 58.

**Step-by-step explanation:**

We are **given the following** in the question:

Mean, μ = 42

Standard Deviation, σ = 8

We are given that the distribution of average number of days between a bill is a bell shaped distribution that is a **normal distribution.**

**Empirical Formula:**

- According to Empirical formula almost all the data lies within three standard deviation of man for a normal distribution.
- Almost 68% of data lies within 1 standard deviation of mean.
- Almost 95% of data lies within two standard deviation of mean.
- Almost 99.7% of data lies within three standard deviation of mean.

Thus, by Empirical formula 95% of data lies within two standard deviation.

**Thus, approximately 95% of the numbers of days will be between 26 and 58.**