An electrically powered conveyor transfers energy to move packages. It is tested under the same operating conditions each time. The input power is 900 W in all three tests.
| Test | Conveyor condition | Useful output power |
|---|---|---|
| 1 | No modification | 540 W |
| 2 | Bearings lubricated | 630 W |
| 3 | Lower-resistance connecting wires fitted | 585 W |
Using the results and your knowledge of energy transfers, explain which modification increases the conveyor's efficiency more.
Your answer should include a prediction of the efficiency if both modifications were made together. For your prediction, assume that each modification reduces the wasted power by the same amount as it did when tested on its own, and that the input power is still 900 W.