A firm has two production departments: Department X and Department Y. Both production departments are supported by two service departments: Department A (i.e. the power department) and Department B (i.e. the maintenance department). Departments A and B also consume service from one another. The work done by Departments A and B is summarized in the table below (work by Department A is in kilowatt-hours; work by Department B is in labor hours). Costs of Department A are $200,000, and costs for Department B are $80,000. What percentage of maintenance department labor hours are consumed by the power department? \begin{tabular}{c} \hline 50% \\ \hline 20% \\ \hline 100% \\ \hline 80% \end{tabular}