Test for Homogeneity · Exercise 8

Do private practice doctors and hospital doctors have the same distribution of working hours? Suppose that a sample of 100 private practice doctors and 150 hospital doctors are selected at random and asked about the number of hours a week they work. The results are shown in.
$$\begin{array}{ccccc}& \text{20–30}& \text{30–40}& \text{40–50}& \text{50–60}\\ \text{Private Practice}& \text{16}& \text{40}& \text{38}& \text{6}\\ \text{Hospital}& \text{8}& \text{44}& \text{59}& \text{39}\end{array}$$

What is the test statistic?

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Introductory Statistics 2e · §11.4 Test for Homogeneity · Exercise 8