A reservoir is emptied every day at a fixed time. After that, either pump X or pump Y, or both together, work to fill the reservoir. On Monday, pump X alone finished filling the reservoir by 9 pm. On Tuesday, pump Y alone finished filling the reservoir by 7 pm. On Wednesday, pump X worked alone till 6 pm, and then pump Y worked alone from 6 pm to 8 pm to complete the filling. At what time would the reservoir be filled on Thursday if both pumps were used simultaneously the whole time?