tried 19.50, this was not correct.

\begin{tabular}{|c|c|c|c|c|c|c|} \hline \multirow{2}{*}{\begin{tabular}{c} Tank \\ Element \end{tabular}} & \multirow{2}{*}{\begin{tabular}{c} Performance \\ Rating \end{tabular}} & \multicolumn{5}{|c|}{ Observation (minutes per cycle) } \\ \hline & & 1 & 2 & 3 & 4 & 5 \\ \hline 1 & 110% & 04 & 0.4 & 07 & 05 & 05 \\ \hline 2 & cos% & os & 07 & 07 & 01 & 00 \\ \hline 3 & & 07 & 05 & & 04 & 05 \\ \hline 4 & os. & 14 & 10 & 10 & 10 & is \\ \hline \end{tabular}