The Number of Degrees of Freedom in a Test of a Contingency

Short Answer

The number of degrees of freedom in a test of a contingency table with 7 rows and 5 columns is: $\begin{array}{|l|l|}\hline\text { A. } & 24 . \\\hline \text { B. } & 35 . \\\hline \text { C. } & 30 . \\\hline \text { D. } & 28 . \\\hline\end{array}$