From the data shown in the table, the weighted mean size (in micrometer, correct to two decimal places) of the sediment population is ............
\[ \begin{array}{|c|c|} \hline \text{Grain Size (micrometer)} & \text{Dry Sediment Weight (in gram)} \\ \hline 4 & 50 \\ 20 & 75 \\ 40 & 125 \\ 60 & 50 \\ \hline \end{array} \]