Considering that we have the standard deviation for the sample, the t-distribution will be used, and the critical value is t = 2.6682.
In this problem, σ is not known, hence we get the standard deviation of the sample from the histogram and the t-distribution is used.
Using a t-distribution calculator, considering a confidence level of 99% and 56 - 1 = 55 df, the critical value is t = 2.6682.
More can be learned about the t-distribution at https://brainly.com/question/16162795