The diagram illustrates how pressure in the left side of the heart and the aorta varies with time. This cardiac cycle lasts $0.6\,\text{s}$. Points $1$, $2$, $3$ and $4$ show when the atrio-ventricular valves and the semi-lunar valves open or close. What is the total length of time in one cardiac cycle for which the atrio-ventricular valves and the semi-lunar valves are both closed together?
- A$0.03\,\text{s}$
- B$0.04\,\text{s}$
- C$0.07\,\text{s}$
- D$0.21\,\text{s}$