Two-Way Frequency Table

Last semester, Mr. Boggs asked all of his students to record the amount of time they spend studying for his chemistry final. He constructed a two-way frequency table of the information. $$\begin{array}{|c|c|c|c|c|c|} \hline &D&C&B&A&\text{Total}\\ \hline 6+&0&1&11&22&34\\ \hline 4-6&1&5&14&17&37\\ \hline 2-4&7&20&11&5&43\\ \hline 0-2&26&10&2&0&38\\ \hline \text{Total}&34&36&38&44&152\\ \hline \end{array}$$