Doctors measure the concentration of cholesterol in the blood of four patients to evaluate their health.
The table below shows four different blood cholesterol categories:
| Blood cholesterol concentration in mmol/dm3\text{mmol/dm}^3mmol/dm3 | Cholesterol category |
|---|---|
| <4.5< 4.5<4.5 | Low |
| 4.5–5.24.5\text{--}5.24.5–5.2 | Normal |
| 5.3–6.35.3\text{--}6.35.3–6.3 | Medium |
| 6.4 and above6.4\text{ and above}6.4 and above | High |
The graph below shows the blood cholesterol concentration of four patients: W, X, Y, and Z.

The blood cholesterol concentration of patient Z is greater than the blood cholesterol concentration of patient W.
Calculate how many times greater.