The following is total monthly budgeted cost and activity information for the four activity centers in the billing department of Oregon Power Company: In September, actual total costs and activity were as follows: \begin{tabular}{|l|c|c|} \hline Activity Center & Total Costs & \multicolumn{1}{|c|}{ Driver Amount } \\ \hline Statement inquiry & $231,388 & 3,050 labor hours \\ \hline Correspondence & $31,452 & 2,540 letters \\ \hline Account billing & $268,369 & 2,560,000 lines \\ \hline Payment verification & $88,591 & 20,670 accounts \\ \hline \end{tabular} Required Payment verification Account billing