A cable-lifting mechanism contains four gears.
| Gear | Number of teeth | Connection |
|---|---|---|
| A | 16 | meshes directly with B |
| B | 48 | fixed to C on the same shaft |
| C | 15 | meshes directly with D |
| D | 60 | turns the cable drum |
Gear A turns anticlockwise at 144 revolutions per minute.
Calculate the rate of rotation of gear D.
State the direction in which gear D turns.
Explain why connecting the cable drum to D, rather than C, helps the mechanism lift a load.